Advanced Marksmanship Can zero change 1moa going from bench to prone?

T

TimK

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Jan 13, 2010
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#1
Got a hard zero the other day at 200 shooting off a bench. Shot again Saturday prone and my zero was off one full moa (impact was low). Conditions were extremely similar except for heavy mirage. As I understand it, mirage should have caused me to hit high, not low. Both sessions I was shooting off a bipod and bag.

The rifle and scope check out OK for loose fasteners.

This is not the first time I've noticed a zero change, but other times I was still screwing around with load development and attributed it to that. I'll often shoot from the bench while load testing, then go prone for practice.
 
#2
Re: Can zero change 1moa going from bench to prone?

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">I'll often shoot from the bench while load testing, then go prone for practice.</div></div>

I wouldn't assume that a zero obtained off a bench was valid prone.

If you want a zero which is valid prone, get it prone. I do load development prone, because I don't shoot off a bench.

Mirage is unlikely to have any effect at 200 yards.
 
#4
Re: Can zero change 1moa going from bench to prone?

You're not holding the rifle the same way. That changes the way the rifle responds to the shot impulse. I saw a guy once who could predict the muzzle velocity on a rifle shot over a chronograph by how much pressure he used holding the rifle in his shoulder.

So, if I want a zero which is valid prone, I shoot prone.
 
#5
Re: Can zero change 1moa going from bench to prone?

In any position there's a relationship between the shooter, gun and ground. This relationship: elbows, stockweld, butt-to-shoulder, grip, and non-firing hand, when consistently controlled, will minimize divergence in recoil angularity between the bore at rest and the bore as the bullet clears it, thus, allowing for a good zero. Once the position is changed or moved, where any of the factors of the steady position become particular to what's new, then a zero change is to be expected.
 
#6
Re: Can zero change 1moa going from bench to prone?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Tim K</div><div class="ubbcode-body">Got a hard zero the other day at 200 shooting off a bench. Shot again Saturday prone and my zero was off one full moa (impact was low). Conditions were extremely similar except for heavy mirage. As I understand it, mirage should have caused me to hit high, not low. Both sessions I was shooting off a bipod and bag.</div></div>
Exactly!! My zero shift is the same as yours from prone to bench. I only shoot off a bench when I can't go prone, which has only been twice. I think the shift is from the rifle coming up more during recoil, and how the rifle comes into your shoulder when shooting on a bench. I learned this the hard way before a match. I needed some work done on my rifle the day before a match at Tac Pro. We made the fix at Texas Brigade, and I zero'd at Mike Lau's range on the bench. I was 1 MOA low the first morning shooting prone, and I missed out on a few points til I adjusted my zero to prone. So there is for sure a difference.
 
#7
Re: Can zero change 1moa going from bench to prone?

Thanks to all for the replies and wisdom. It's nice to know I'm not crazy, and there is not some unknown gremlin in my system.

I have a match coming up in two weeks, so I'll be sure to get a new zero beforehand.

As an aside, this endeavor is far more complicated than it appears. When I decided to get into precision shooting, I thought you just worked up a load and then sat behind the rifle. Who knew I would be making new, major discoveries every trip to the range? I've been at this now for just a few months, and it seems like my knowledge and understanding doubles every week. I wonder what else I don't know...

Thanks again.
 
#8
Re: Can zero change 1moa going from bench to prone?

if you adjust your parallax correctly you're zero should not change to a noticable degree... the parallax in the scope is what helps adjust for the change in cheek weld from one position to another, basically turning your scope in to an Aimpoint.

If you didn't take the time to adjust your parallax and your position changes, you get a bold shift.

I on the other hand don't have a shift except when I change my hand position at the end and screw the trigger up. Otherwise, no change in zero from position to position.

<object width="425" height="350"> <param name="movie" value="http://www.youtube.com/v/FVYHIXra4rA"></param> <param name="wmode" value="transparent"></param> <embed src="http://www.youtube.com/v/FVYHIXra4rA" type="application/x-shockwave-flash" wmode="transparent" width="425" height="350"> </embed></object>

video speaks louder than words in this case... I shoot the same target right handed, left handed and from a bench both left and right handed.
 
#9
Re: Can zero change 1moa going from bench to prone?

I've never logged a difference in zero from bench to prone. I have, however, logged a zero change during a two-day or three-day course after firing a few hundred rounds.
 
#11
Re: Can zero change 1moa going from bench to prone?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">if you adjust your parallax correctly you're zero should not change to a noticable degree... the parallax in the scope is what helps adjust for the change in cheek weld from one position to another, basically turning your scope in to an Aimpoint.

If you didn't take the time to adjust your parallax and your position changes, you get a bold shift.

I on the other hand don't have a shift except when I change my hand position at the end and screw the trigger up. Otherwise, no change in zero from position to position.

video speaks louder than words in this case... I shoot the same target right handed, left handed and from a bench both left and right handed. </div></div>

Well, crap. I thought I had parallax adjusted, but maybe I didn't. I'd love to get off the vertical portion of the learning curve sometime soon...
 
#12
Re: Can zero change 1moa going from bench to prone?

Lots of things can account for a 1 MOA difference.

Old martial arts saying: "Failure is easy to handle - work hard to improve. Success is easy to handle - you didn't solve all the problems yet, so work hard to improve."
 
#13
Re: Can zero change 1moa going from bench to prone?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Outsydlooknin75</div><div class="ubbcode-body">Frank, that video is hillarious ..</div></div>

I'm with you on that one.
 
#14
Re: Can zero change 1moa going from bench to prone?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body">Lots of things can account for a 1 MOA difference.

Old martial arts saying: "Failure is easy to handle - work hard to improve. Success is easy to handle - you didn't solve all the problems yet, so work hard to improve."
</div></div>

Indeed
 
#15
Re: Can zero change 1moa going from bench to prone?

Different animal moving away from irons... if you are spending $3k on a rifle and $2k in on scope and your zero shifts from prone to a supported position what is the point of the whole thing ?

A tactical rifle needs to be well suited for tactical applications which have nothing to do with range shooting. The operator must be able to move from position to position under varying conditions and hit their target, and not just E Types but partially obscured targets. If common wisdom of tactical shooting was that your zero shifted with every changing condition the discipline wouldn't exist in its present form and things would be taught differently. A good example of this happens in every tactical based competition out there. Nothing is standard and each stage is slightly different from the one before. In fact we have run one such match which only had 1 prone shot, everything else was from position.

Cheek weld, while of utmost importance with iron sights is not nearly as critical with a scoped rifle providing you, 1.) properly adjust the parallax and 2.) maintain perfect edge to edge clarity.

In regards to parallax, the job of the parallax adjustment is to bring the Target, the Reticle and the Shooter's Eye on the same Focal Plane. This is key, it's essentially telling you that the scope becomes an Aimpoint type system. Having all three of these things on the same focal plane is an important distinction. Imagine a target on a wall and hold a pencil in front of you with the tip acting as the reticle. if you move your head the target moves behind the pencil. Now take that same pencil and touch it to the target and move your head... pencil stays in the middle of the target where you touched it. That is parallax adjustment and moving the pencil to the target puts it on the same focal plane.

The most common error when moving from position to position is the relationship between the scope and the eye. If you don't have positive edge to edge clarity you risk causing a shift, especially if you have not properly accounted for parallax. Any shadowing can cause a shift in impact, combined with parallax as much as a 1.5 MOA at 100 yards.

The rifles are designed not change zero with something as simple as a change in position, it's just not a practical to expect this to happen. Shooting from varying alternate positions is the heart of the tactical shooter, anyone can shoot these things from the prone. A rifle sensitive enough to be affected by small changes in the shooter's position is really unsuited for tactical applications.
 
#16
Re: Can zero change 1moa going from bench to prone?

Frank,

Here's the fact to start with, consistent geometry from consistent control will always determine the zero's reliability. Change the position in any manner which changes recoil, that's to say, which will change the angularity from the bore at rest and the bore as the bullet clears it and the bullet will not go where aimed, period. What kind of rifle you've got and for what purpose you're using it is moot-physical law does not care, although a relatively heavy rifle and/or low recoiling cartridge is influential. Now, if you can control your rifle from all sorts of positions with such consistency that there's no divergence in angularity from the bore at rest and the bore as the bullet exits, O.K., that's real good.

 
#17
Re: Can zero change 1moa going from bench to prone?

Frank writes:
"The most common error when moving from position to position is the relationship between the scope and the eye. If you don't have positive edge to edge clarity you risk causing a shift, especially if you have not properly accounted for parallax. Any shadowing can cause a shift in impact, combined with parallax as much as a 1.5 MOA at 100 yards."

This is the most common cause I have found that causes the POI shift when going from bench to prone or any other position.

Bench to prone should cause the least amount of shift, because both are the most stable positions you can get it. Too many people who set up a scoped rifle on the bench and shoot it on high X have the scope too far back for shooting prone and the edge to edge clarity is lost and shadowing occurs when going prone.
This generally because your head moves forward on the stock when going prone.
Sometimes moving the scope forward one pic rail slot solves this problem but reqires a slight change in bench head position.
 
#18
Re: Can zero change 1moa going from bench to prone?

Of course, sight misalignment, irons or scope, being angular, will increase bullet displacement with distance. Add failure to adjust NPA (assuring recoil divergence) and then you're describing someone who does not likely know there's a difference between executing the firing task and actually knowing how to shoot. Only when the target is so big or close to be hit intuitively is executing the firing task and knowing how to shoot synonymous.
 
#19
Re: Can zero change 1moa going from bench to prone?

You get that eye relief issue also when using a rifle set up for prone in other positions.

For that reason, I set my rifles up so that I have a bit of stretch to the proper eye relief when prone, and then I have better eye relief in other positions.
 
#20
Re: Can zero change 1moa going from bench to prone?

Eye relief is of course greatest in the standing position and closest in prone. Interestingly, with peep sight, the standing position yields a much smaller and darker sight picture when stockweld is placed appropriately, as compared to the sight picture in prone when the stockweld is relaxed. Any size picture can work and that's good since one size does not fit all.
 
#21
Re: Can zero change 1moa going from bench to prone?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body">You get that eye relief issue also when using a rifle set up for prone in other positions.

For that reason, I set my rifles up so that I have a bit of stretch to the proper eye relief when prone, and then I have better eye relief in other positions.
</div></div>

You are absolutely correct in this and we set up our rifles the same way, you and I, probably for the same reason...
 
#22
Re: Can zero change 1moa going from bench to prone?

We drive the rifles different for different positions and describe it as driving a porsche versus driving a truck. Both get you to the same place but you drive each one slightly different. Knowing your support is some what compromised as you move off the ground it is indicative of the shooter to understand he must drive the rifle slightly different to control the rifle properly.

We routinely spot our own impacts even from supported kneeling and standings positions because we understand we need to drive the rifle differently. There should be no angular change as you adjust your control accordingly. We don't loose control of the rifle thinking we can limp wrist like some will do with their light competition triggers.

Right handed, left handed, prone, sitting, kneeling, standing, it is all the same as far as my zero is concerned, the rifle doesn't know any better, it just requires me to drive it correctly. This is why we feel it is important to <span style="text-decoration: underline">zero the rifle</span> and <span style="font-style: italic">not zero the shooter.</span> When you zero your flinch, or your lack of trigger control you change that zero with each position.
 
#23
Re: Can zero change 1moa going from bench to prone?

Not zero the shooter? The sight or sights, unless they're broken or loose, are always in alignment, that's to say, they always have a consistent relationship with the line of bore. The zero is all about the shooter, his consistent control of the firearm until recoil has subsided.

Take the bipod off the rifle and sling-up. Then see if you can maintain a zero at any distance/position if any aspect of your relationship between you, the gun, and the ground changes-even on successive shots from the same position. Full contact requires perfection if the idea is to put all rounds right-in-there. At, let's say, a 100 yard target in no wind conditions with a match grade rifle and match grade ammunition every shot should go through the same hole, just as that of the first round if the position is steady, right? Benchresters can do it regularly, free recoil. Of course, unless it's free recoil from the bench, one hole groups are not likely possible because indeed the position is not identical shot after shot. The bottom line is simply this, if you can shoot from different positions and not need to adjust the sight you're likely accepting what the task requires which is something less than perfection.

Here's another example, you shoot at any distance from a no wind condition and the bullet hits-pinwheel X. I'd say you're pretty well zeroed. The second shot goes to the left of the first shot. Are you still zeroed? You'd say yes, but, nevertheless, you did not hit where aimed. The gun could still be considered zeroed, but, of course, control needs to get back to where it was for the first shot. That's doable, but change from prone to standing or prone to sitting and getting identical control over the gun is just not likely. What's more likely is proper control will be somewhat different, creating angular divergence (compared to the previous position) from the bore at rest and as the bullet clears it; and, that will mean an adjustment of zero for best results. Sure, the realities of anything but perhaps competitive target shooting at the highest level either do not demand or allow for so many zeros, and, in fact it may be good enough to just adjust for wind to get a good hit.

If my score book shows that my 100 yard prone is 7 up and 2 right, which when used for sitting produces a group a half inch low and a half inch to the right, what do I do. Do I think gee I guess I need to control the gun the way I did prone, leaving the sights alone. Yeah right. I'm not going to do that because, one, my body can not be made to contact the gun and ground in sitting as it does in prone, and, two, I don't need to. I can just re-zero for the position.

BTW, most folks don't have the skill to put all of their shots in one hole, so understanding when the rifle is zeroed is somewhat sketchy at best. Only through blind plot and call excercises can a zero be refined to clearly know where the barrel is pointed.
 
#25
Re: Can zero change 1moa going from bench to prone?

I must be doing something right because mu zero does not change much (less than 0.4 MOA?) when shooting prone or bench... recoil control, cheek position, bipod hop, etc. change but zero does not. Same for shooting with the bipod over a hard vs soft surface.

Note I'm not talking about minute changes like in benchrest.

I'm with LL, with a scoped rifle:

"Right handed, left handed, prone, sitting, kneeling, standing, it is all the same as far as my zero is concerned, the rifle doesn't know any better, it just requires me to drive it correctly. This is why we feel it is important to zero the rifle and not zero the shooter. When you zero your flinch, or your lack of trigger control you change that zero with each position."
 
#26
Re: Can zero change 1moa going from bench to prone?

You don't think a .4 MOA change is different? Tell ya what. Shoot your rifle prone with sling, about twenty rounds, then, follow up without any change in sight adjustment with about 20 rounds sitting position with the sling. Come back here and tell me whether you have one or two groups on your target. Am betting there will be two.
 
#27
Re: Can zero change 1moa going from bench to prone?

I guess we'll have to do a video, because we don't see the changes you are talking about.

The call to, <span style="font-style: italic">"Take off the bipod"</span> is silly, we do take off the bipod and will shoot slung even though we consider it a legacy skill with little practical application in tactical shooting. Forget the fact it is slow to get into and out of effectively, we feel that given the time and opportunity one should always support the front of the rifle, and in doing so, we don't see a shift in zero. If you can sling up and hit a target at 400 yards faster than I can with my bipod, more power too you. But I have to tell you, during the Dot Drill we do, which is standing to prone on a sub MOA dot targets we start with a time limit of 15 seconds and reduce the time to 6 seconds for 1 shot from standing to prone. People clean this drill, with a 6 second time limit.

As well, last week we had a government class, and Jacob demo'd shooting from the kneeling using just the sling, and guess what he centered punched the 10 ring on a 2" shooting C, he experienced no change in zero. There is also a declaration on the wall at RO talking about the single shot hit on the 1000 yard target at Tac Pro that he hit with his AW from the standing. He didn't sling up either, he pulled it off unslung.

We have also heard that no two shooter will have the same zero, yet we see it all the time. In fact my zero and Jacob's zero is exactly the same. We use each others rifles all the time, no difference. he is 6ft tall, I'm not. We zero the rifle, not the shooter.

I can shoot slung, unslung, etc, I went with Leo in CO and shot the .22 comp which was slung in a jacket, did pretty well. In fact I shoot prone slung being straight behind the rifle, no angle off to the side. During my time in the USMC I was a 5th award expert, so I have a background in this stuff, and can tell you, we don't see it the same way you do, it might be different in your discipline, but what you are saying doesn't follow suit with tactical shooting, and we aren't settling for large deviations.

If what you are saying is true, nobody should be able to shoot from the support side with the same zero, yet we do it and see it every class. Left handed, right handed, positional, it makes no difference.

Now, you can change the rules and talk about 1 hole, but practically speaking, I am talking 1/2 MOA to 1 MOA at 100, which is a realistic goal with any tactical rifle from positions other than prone. If you want to talk benchrest groups, go talk to benchrest shooters, but this is field shooting and there is a practical limit to field shooting. Which is also why I have no interest in taking my bipod off, the sling is slow, and not a practical application of a tactical rifle. Can you be accurate, absolutely as described, shooting the center of a 2" shooting C is good from the kneeling in anyone's book, and was done with a rifle not designed for sling shooting.

Try removing your sling, taking off your iron sights and pick up a bipod and a scope, you might see things a bit different. The angularity of the irons are the reasons we don't shoot irons anymore. You're positional changes move the angle of attack on the iron sights, however that is not a concern with my scope when I have edge to edge clarity and the parallax adjusted out. The bullet will go where the reticle is pointed, the rifle is supported, and it is designed not to be influenced as much as you describe.
 
#28
Re: Can zero change 1moa going from bench to prone?

Im in the same boat here as Frank, my rifle is zeroed and ive had plenty of people hop down behind my gun and the POI is the same place as my POI. Same thing goes for positional shooting as well.

Sterling Shooter, It seems that your arguement always favors the skill set found in NRA Service Rifle which is cool and all, but not what the site is about. Slinging up when i have the option to fold a bipod out and be a whole lot more stable is just senseless. As for the shooting Prone then shooting Sitting, the only factor for any of my shots not being where the rifle was zeroed lays soley on my shoulders and not the zero of the rifle
 
#29
Re: Can zero change 1moa going from bench to prone?

Frank,

O.K. shoot prone with bipod, then shoot, sitting with non firing hand on the handguard instead of bipod, shoot plenty of rounds from each position at the same aiming point, the X ring of let's say an MR-31. I'll bet with you too, when the dust settles and the smoke clears, you'll have two distinct groups, one of which will not be right-in-there and not as high in X count.

Shooting at LR prone to win requires perfection in every aspect of shooting. Taking this perfection to 100 yard XC reveals indeed that there is a POI change when the position changes, as well as when the position within the position changes, physics would have it no other way. Thing is, and I'm not talking about you, most shooters shooting at even an Expert level can't recognize whether they've got a real good zero or not. Their groups are two big to understand anything exactly. One thing for sure, if I changed position and did not account for a .4 MOA change in POI, as mentioned by another poster here earlier, I would come up with a very small X-count. For me, something like a .4 MOA change in POI will demand a sight adjustment. Thank goodness for 1/4 minute click value, and even then I sometimes wish it were finer.

Now, all this stuff about your shooting being different than mine, It's all the same, only the motives are different.
 
#30
Re: Can zero change 1moa going from bench to prone?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: deadly0311</div><div class="ubbcode-body">Im in the same boat here as Frank, my rifle is zeroed and ive had plenty of people hop down behind my gun and the POI is the same place as my POI. Same thing goes for positional shooting as well.

Sterling Shooter, It seems that your arguement always favors the skill set found in NRA Service Rifle which is cool and all, but not what the site is about. Slinging up when i have the option to fold a bipod out and be a whole lot more stable is just senseless. As for the shooting Prone then shooting Sitting, the only factor for any of my shots not being where the rifle was zeroed lays soley on my shoulders and not the zero of the rifle</div></div>

I'm responding to the OP's question, heck, if there were just posts within what this site is about, I doubt this thread would have ever appeared, as there is nothing particularly tactical about it.

Oh, and one more thing, you might want to look at the definition of zeroing. It means adjusting the sights to hit where aimed. If you're not hitting where aimed you're either not zeroed or you do not have a consistent perspective/control of aim.

BTW, the purpose of any position is to support the principles of marksmanship. The idea is to transfer the stability of the ground into the position through bone and artificial support. A bipod in prone may or may not come to the shooter's aid. That's why the ability to shoot from other positions with or without artificial aids to bone is a good idea.

You mentioned using the bipod when you have the option, Right now, I'd guess you have the option to control every aspect of your shooting: support, target size, distance to target, most everything except perhaps for wind. Is that tactical?
 
#31
Re: Can zero change 1moa going from bench to prone?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Sterling Shooter</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: deadly0311</div><div class="ubbcode-body">Im in the same boat here as Frank, my rifle is zeroed and ive had plenty of people hop down behind my gun and the POI is the same place as my POI. Same thing goes for positional shooting as well.

Sterling Shooter, It seems that your arguement always favors the skill set found in NRA Service Rifle which is cool and all, but not what the site is about. Slinging up when i have the option to fold a bipod out and be a whole lot more stable is just senseless. As for the shooting Prone then shooting Sitting, the only factor for any of my shots not being where the rifle was zeroed lays soley on my shoulders and not the zero of the rifle</div></div>


Oh, and one more thing, you might want to look at the definition of zeroing. It means adjusting the sights to hit where aimed. If you're not hitting where aimed you're either not zeroed or you do not have a consistent perspective/control of aim.

BTW, the purpose of any position is to support the principles of marksmanship. The idea is to transfer the stability of the ground into the position through bone and artificial support. A bipod in prone may or may not come to the shooter's aid. That's why the ability to shoot from other positions with or without artificial aids to bone is a good idea.

<span style="font-weight: bold">You mentioned using the bipod when you have the option, Right now, I'd guess you have the option to control every aspect of your shooting: support, target size, distance to target, most everything except perhaps for wind. Is that tactical?</span> </div></div>

you'd be wrong about the bold part, been plenty of times were a folding the bipod out wasnt a viable option, and if that option were chosen id be laying in a wood box and not typing this. Im fairly certain i have a pretty solid understanding what "zeroing" a rifle is. I was stating that if i move from postion to postion and the shot isnt the same POI its not that the zero changed, its that my postional shooting isnt where it should be in terms of perfection. Again, i wasnt trying to get into a pissing match with you about anything nor disciplines of shooting that differ from you to me. Most of my shooting now is @ Tactical matches that i have no control over anything other than me, before it was in foreign lands. But having a different zero for a different position doesnt hold water with me, even shooting the USMC rifle qual with iron sites, my cheek weld was as exactly the same as it could be and i never experienced different zeros other than moving yard lines, been a 4 time expert at it to, and never had "2 distinct" groups when going from sitting/kneeling/standing all slung up
 
#32
Re: Can zero change 1moa going from bench to prone?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: deadly0311</div><div class="ubbcode-body">



I was stating that if i move from postion to postion and the shot isnt the same POI its not that the zero changed, its that my postional shooting isnt where it should be in terms of perfection. </div></div>

Really, you just confirmed my whole argument. Thank you. When the position changes within the position you can in effect choose a zero by being consistent with one thing or another, you just need to pick something. Choosing something muscularly relaxed is always a good idea. However, when you go from one position to another is the position not physically different, it obviously can be distinguished from the other. For example, I can see a difference between someone in the standing position and someone in prone. Now, if just a little less than perfection in the position within the position will cause a POI shift, as you alluded to, don't you agree that changing the whole position might do the same. You can be sure it does. And, if you were shooting at a more critical target than what you've been shooting at you would come to see it clearly.

Regarding your Expert qualifications, good for you, but getting good hits on a qualification target is not the equivilant of high X-count cleans in bullseye competition. You're comparing apples to oranges. These shooting tests do both require an understanding of marksmanship but are nevertheless too unrelated to make me think Expert in one would yield an Expert result in the other no matter which arena you were going to or moving from.

Regarding qualifications and ratings, you can of course choose to refine the zero or not refine the zero according to your perceived need to get a good hit. You and Frank will do it as you want, heck I don't care. But, for me, refining the zero has proven to get me better results in the type of shooting competitions I enjoy. If sighting shots or any other indicator suggests I need to adjust the sight to better hit where aimed I'm going to exploit it. Too many new competitive shooters loose easy points because they fail to refine the zero.
 
#33
Re: Can zero change 1moa going from bench to prone?

Lot of talking about how you do it and nothing to demonstrate the differences other than -- its' different for you, but when others come on here and say they record no change you latch onto one line when someone says they might see something less than .4 MOA, that is the flag you fly.

I have extra days here to do nothing but make videos after this class is over.

We'll make a real video and not one where I am just goofing around, the video will speak louder than words and when the dust settles we'll see if we have 2 different groups or not.

We often find there are those who talk about things that happen to them, but few others who claim these things as law, but it make no sense. it makes no physical sense for the POI to change from position to position unless the shooter is failing on some level, but those same changes would occur if they screwed it up in the prone too. So we'll just make a video and move all over the rifle being sure to employ proper fundamentals and ensure edge to edge clarity with the parallax adjusted and we'll how much it changes. My bet is none, because we have done this before and we do it every class and every competition -- its called the Barricade drill, if changes were normal, people would see it, and they don't.

This isn't Hi Power shooting with iron sights,
 
#34
Re: Can zero change 1moa going from bench to prone?

I've shot both disciplines in my short life. I have shot Small Bore since 1968 and High-Power since 1974. NRA Instructor since 1981.

I have seen exactly what Frank talks about on the iron sight change of seen perspective and exactly what Sterling says about the minute small change. Both Freak and Sterling are saying the same thing, the change Frank sees causes the sight change Sterling adds. I have been there and done that before for 30+ years.
To me it is NOT an issue.

I have been on a scoped rifle looking at people give or take 30 years. I see exactly what Frank sees
"however that is not a concern with my scope when I have edge to edge clarity and the parallax adjusted out. The bullet will go where the reticle is pointed, the rifle is supported, and it is designed not to be influenced as much as you describe".

I see this every Sniper training session we do. It is a fact that does not change and all my years of High Power reinforce that fact.

I do see MY people have a change in their scope setting WHEN they lose the edge to edge clarity and have a shadow they don't recognize when they shoot under high stress and extreme speed, when they can't support the front end of the rifle like Frank talks about.
Frank qualifies his position with the statement
"we feel that given the time and opportunity one should always support the front of the rifle"
and many of our training scenarios DO NOT give you the time or opportunity to do this, based on the recorded 279 shootings in 27 years that ASA took the time to collect and dissect to use for police Sniper training.

This is not worth arguing about, yes, you CAN see a change going from bench to prone, but it 99% will be caused by the scope shadow you don't recognize because you don't have edge to edge clarity because you didn't know to look for it. It IS some shooter error with the scoped rifle...
 
#35
Re: Can zero change 1moa going from bench to prone?

I have found that the POI can change from shooting prone to shooting off a solid wooden bench with some rifles. The other day I also found out something else!

I was field shooting prone at 980 yards with a .338 Edge off a bipod. The rifle was shot off a mound of loose and very soft dirt. On firing the rifle I noticed that I was hitting 2 MOA lower than expected.

This was interesting, as with the wind the way it was, I would have expected some lift rather that extra drop. I thought about it for a while and considered a number of things including parallax, cheek weld etc. I then considered my rifle set up and the possibility that the soft dirt under the Bipod could be collapsing under the recoil of the big .338 causing POI to be low.

I placed some carpet under the Bipod legs to spread the load and continued shooting.
All shots were now back up about 2 MOA and at the expected height on the target.

This is just an observation. Its great when you learn something new.
 
#36
Re: Can zero change 1moa going from bench to prone?

Sterling Shooter,
I dont think that i confirmed anything that you are arguing. I confirmed that my positional shooting sucks. But again a scoped rifle that is properly zeroed will not have a POI change when moving postions. Why do i need to "refine the zero when moving from postion to postion" if its not the zero but rather a flaw in my shooting technique? Why fix the gun/optic instead of fixing the shooter? That would be similar to puting a muzzle brake on a rifle to correct poor form, would it not? So by your arguement of "perfect form" you refining your zero is making up for your lack of form and skill, no?
 
#37
Re: Can zero change 1moa going from bench to prone?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: deadly0311</div><div class="ubbcode-body">Sterling Shooter,
I dont think that i confirmed anything that you are arguing. I confirmed that my positional shooting sucks. But again a scoped rifle that is properly zeroed will not have a POI change when moving postions. Why do i need to "refine the zero when moving from postion to postion" if its not the zero but rather a flaw in my shooting technique? Why fix the gun/optic instead of fixing the gun? That would be similar to puting a muzzle brake on a rifle to correct poor form, would it not? So by your arguement of "perfect form" you refining your zero is making up for your lack of form and skill, no?</div></div>

I'm not suggesting you refine your zero, unless it's in some sort of competition where you have the time to to it. For anything practical it would be worthless.
 
#38
Re: Can zero change 1moa going from bench to prone?

As much as it pains me to agree...
wink.gif


I've seen *some* POI change when going from sighted in on a bench, to shooting from prone. Both off a bipod.

It may be an individual shooter issue, but I feel it is related to how much of 'me' I get behind the rifle when in the different positions.

Shooting from a bench, the fore-end isn't gripped rigidly and only a portion of the upper torso, specifically the shoulder is behind the gun. This is functionally (in my mind) closer to Offhand/Standing, as opposed to when I go prone (with a bipod) where I have my whole (considerable!) body mass in line behind the rifle. Prone with a sling is a whole 'nother ball of wax.

It's not a lot... maybe 1/2 - 1 moa @ 500-600yds. There are a whole bunch of things that can put a shooter off a little (few inches) at distance for their first shot or two of the day from a cold barrel, so I can't / won't say that the little change I see is directly connected with absolute certainty... but it is my belief, FWIW.

As for the video... just a suggestion: Pick a shooter not involved in this thread, don't tell them why you want them to shoot from two different positions, etc. Just have them shoot, and see where things go. Otherwise, there is potential for 'leading' them along to where the results could be influenced one way or another.
 
#39
Re: Can zero change 1moa going from bench to prone?

You alluded in your experience the change in POI was minor. Maybe that is what I could have stressed. Yet, in shooting at targets with very small X rings relative to distance, a 1/4 minute change in POI,, with my position change, is very relevant. Looking at my most recent results for a 100 yard reduced course tournament, I see that my corrected standing zero is just 3/4 minutes different than my corrected prone zero. Sitting is only a 1/4 minute from prone. Certainly, in the context of tournament shooting I could shoot all matches with one zero, probably, the one established from prone, and, I'd likely still have a good score. Thing is. I want the highest score, and, not to refine the zero would just be to not capitalize on an asset-my skill to consistently center things/hold hard.

At any rate, I appreciate your input, as much as it pained you. Ideas about good shooting today are a mix of fact, theory, and myth. The truth is often a product of perspective. I'm quite comfortable with my observations, as I am sure Frank is of his record of events.

BTW, my quarter minute sight correction is worth about a half minute change at target, after all I'm shooting with irons, which is more about a perception of consistent hold than a reality of it, as possible with some sort of optic.
 
#40
Re: Can zero change 1moa going from bench to prone?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">I guess we'll have to do a video, because we don't see the changes you are talking about.

The call to, <span style="font-style: italic">"Take off the bipod"</span> is silly, we do take off the bipod and will shoot slung even though we consider it a legacy skill with little practical application in tactical shooting. Forget the fact it is slow to get into and out of effectively, we feel that given the time and opportunity one should always support the front of the rifle, and in doing so, we don't see a shift in zero. If you can sling up and hit a target at 400 yards faster than I can with my bipod, more power too you. But I have to tell you, during the Dot Drill we do, which is standing to prone on a sub MOA dot targets we start with a time limit of 15 seconds and reduce the time to 6 seconds for 1 shot from standing to prone. People clean this drill, with a 6 second time limit.

As well, last week we had a government class, and Jacob demo'd shooting from the kneeling using just the sling, and guess what he centered punched the 10 ring on a 2" shooting C, he experienced no change in zero. There is also a declaration on the wall at RO talking about the single shot hit on the 1000 yard target at Tac Pro that he hit with his AW from the standing. He didn't sling up either, he pulled it off unslung.

We have also heard that no two shooter will have the same zero, yet we see it all the time. In fact my zero and Jacob's zero is exactly the same. We use each others rifles all the time, no difference. he is 6ft tall, I'm not. We zero the rifle, not the shooter.

I can shoot slung, unslung, etc, I went with Leo in CO and shot the .22 comp which was slung in a jacket, did pretty well. In fact I shoot prone slung being straight behind the rifle, no angle off to the side. During my time in the USMC I was a 5th award expert, so I have a background in this stuff, and can tell you, we don't see it the same way you do, it might be different in your discipline, but what you are saying doesn't follow suit with tactical shooting, and we aren't settling for large deviations.

If what you are saying is true, nobody should be able to shoot from the support side with the same zero, yet we do it and see it every class. Left handed, right handed, positional, it makes no difference.

Now, you can change the rules and talk about 1 hole, but practically speaking, I am talking 1/2 MOA to 1 MOA at 100, which is a realistic goal with any tactical rifle from positions other than prone. If you want to talk benchrest groups, go talk to benchrest shooters, but this is field shooting and there is a practical limit to field shooting. Which is also why I have no interest in taking my bipod off, the sling is slow, and not a practical application of a tactical rifle. Can you be accurate, absolutely as described, shooting the center of a 2" shooting C is good from the kneeling in anyone's book, and was done with a rifle not designed for sling shooting.

Try removing your sling, taking off your iron sights and pick up a bipod and a scope, you might see things a bit different. The angularity of the irons are the reasons we don't shoot irons anymore. You're positional changes move the angle of attack on the iron sights, however that is not a concern with my scope when I have edge to edge clarity and the parallax adjusted out. The bullet will go where the reticle is pointed, the rifle is supported, and it is designed not to be influenced as much as you describe. </div></div>

Bingo!!!!!!!!!!!!!!!
 
#41
Re: Can zero change 1moa going from bench to prone?

<span style="font-style: italic">I have an Army Marksmanship Unit Countersniper Guide from 1980, so old in fact they cover both iron sights and "telescopic sights" where the reticle choices don't include a mil dot because they weren't available yet. You basically can chose a Duplex or a Post reticle that is it.</span>

In Chapter 3 page 7 of the Guide, under "Sights" they write:

2. In order to prove the requirement for an optical sight on the part of the countersniper, a comparison of hte characteristics of all types of sights available today will be made.

a. The open sight is found on most .22 caliber rim fire rifles and many hunting rifles when received from the factory. This type of sighting system requires the shooter place his head and eye in the exact position in relation to the sight to insure that they are all properly aligned. He must focus on the rear sight, the front sight and the target at various times in the firing of each shot. In as much as it is physically impossible for the human eye to focus on more than one of these objects at any one time, his eye must shift focus from the rear sight, to the front sight, to the target. In the course of obtaining a good "sight picture" this process is actually run through several times in the firing of a single shot. Experience in competitive shooting has shown that the best results are obtained by firing with the front sight sharply in focus and allowing the rear sight and target to be out of focus. Immediately note a disadvantage to this system in the use of moving targets since there is a tendency to look directly at the target and consequently accept a loss of accuracy. Another objection to the open sight system is the fact it covers up the target, to the degree that nothing below the top of the rear sight can be seen when aiming. Additional Targets, which certainly could be danger points, are obscured by the sights. (See figure 3)

b. The peep sight is a much more precise aiming device than the open sight and requires the eye to focus on the front sight and the target. Again, the best results are obtained while concentrating focus on the front sight. However, many people well tend to drift into the lower half of the aperture of the peep and consequently shoot low. The light passing through the aperture is much lower in intensity than the available light and many times objects that can be seen clearly with the naked eye cannot be defined by looking through the sights. The field of view which is defined as the area that can be seen through the peep sight, is limited. In fact, it is much smaller in size than the area that is viewed through telescopic sights of the magnification levels with which we are concerned. Further, good peep sights are expensive and cost almost half as much as an acceptable optical sight which does the job much more effectively. (See figure 4)

3. From experience it has been determined that the telescopic sight is the only suitable sight to be employed in the countersniper role. In shooting, you simply look into the eye piece of the telescope, place the reticle on the target and squeeze the trigger.

4. After the Countersniper has initially zeroed the weapon, it is his responsibility to record and maintain this zero....


<span style="font-style: italic">It goes on to talk about Parallax which I will come back too, however on page 18, Chapter 5 General: </span>

1. Effective Shooting

a. No standardization of firing positions can be established for the countersniper as there are for the competitive marksman. The basic fundamentals of aiming, positions, and trigger control that can be found discussed in detail in any marksmanship manual apply to either a competitive shooter or a countersniper.

c. The most important and also the most difficult fundamental to master is trigger control. The majority of misplaced shots stem directly from the improper application of trigger control.

d. A highly accurate zero must be obtained. This can be accomplished with the aid of some type of supported position using sandbags or a bench rest.


<span style="font-style: italic">Point of this... no mention of a change in zero per position, and no standard position established. Might be clue here, even being 30 years old. </span>

Now, back to parallax, which is the longest section, Page 10, section d.

Parallax:
This is a term shooters hear of but seldom understand. When a shooter has trouble with the zeroing or grouping characteristics of his rifle, some friend will as. "How's the parallax ?" Not wishing to display ignorance, he will invariably reply, "It's ok", when in reality he doesn't know what it's all about. When you look into the eye piece of the telescope, the reticle and the image should appear on the same focal plane. If the scope has plain cross wires, the wires should appear as though they were drawn on a photograph and should not require a shifting of the focus of the eye to see each one separately.


<span style="font-style: italic">They go on to talk about Parallax again, and how to test and what it looks like, then this: </span>

<span style="font-weight: bold">What does all this add up to ? It simply means that if your eye is looking into the right side of the eye piece you shoot on one side of the target and with your eye on the left you shoot on the other side. The of the impact is changed by the position of the eye when using a telescope with parallax error, but it is not influenced by the eye movement on a correctly adjusted telescope. </span>


<span style="font-style: italic">This is quoted out of the Guide put out by the AMU... </span>
 
#42
Re: Can zero change 1moa going from bench to prone?

Frank,

Let's back up here a minute. I'm not going to persuade you, that's for sure; but, as earlier posted, I see that it's advantageous to refine my zero when I've changed my position. It's not anything to do with sight alignment or trigger control, I've got the basics. It's about every different position having elbows, butt-to-shoulder, stockweld, grip, and non firing hand in a different relationship with the rifle and ground as required for muscular relaxation, and recognizing that each of these unique relationship's produces a recoil peculiar to the position. The peculiarity is what determines what zero refinement is necessary from the initial prone zero. Sure, I can zero my gun from a very steady prone position and use that zero for any sort of forced target/position and, by a military measure, get very good hits; but, by refining the zero, based on apparent corrections necessary, I can get better scores and higher X counts.

Now, from what I gather, this perfection, inspired by competition, is moot in most any kind of real world stuff; nevertheless, when shooting targets with little bitty X rings it helps. I think for any shooter here who has the basic marksmanship skill to produce a zero-able group, shooting strings from standing, sitting, kneeling, and prone will reveal the usefulness for zero refinement when shooting scoreable targets. And, rather than relying on what either you or I deem proper, these curious shooters can see for themselves the impact, no pun intended, the effect of position change makes on bullet placement.
 
#43
Re: Can zero change 1moa going from bench to prone?

Sterling,

I understand what you are saying, but I have to disagree, think about it realistically. How much different is the hold on the stock from Sitting to Kneeling ? Not much if at all, the contact is essentially the same. If you're zero is changing one of two things are happening... the angle on the sights have changed accounting for the zero shift, or your rifle has a bedding issue where the flexing on the stock is effecting your point of impact. (Or with service rifle, the handguards are flexing under sling tension)

There is no way changing positions from sitting to kneeling is producing a shift in impact unless the shooter is causing it unknowingly as with a compromised sight picture.

As I stated, we will shoot a video, plain and simple, slung, and with a bipod with our tactical rifles. Rifles don't change zero unless the shooter is negatively influencing them, and the hold on the rifle from sitting to kneeling is not enough to cause that change, and honestly prone either... it's still 3 points of contact, head, and hands... where is this big divergence ? some people will also address the trigger differently which is another negative affect but that should not cause an elevation issue unless they are sympathetically squeezing the trigger and pressing their shoulder forward, which would be some what masked in a prone position.

The only place I can see a person changing this, as you describe is, if they go from a prone position on the ground to a free recoil position on the bench. That is different, but a supported positions is a supported position. This is why we free float barrels, handguards, etc... so you don't get changes do to uneven pressures on the rifles we shoot. Moving your hand 2 inches on the stock forward or back is not going to cause a shift if it is properly built and bedded.

I have been clear how the disciplines differ, and I am not here to tell you how to shoot hi power, but you can't tell me this is same with tactical shooting either. We do it daily. What you are experiencing is pretty unique to you, and does not follow the rules of common sense for me. We shoot withe bipod, rifle stock supported, unsupported, slung, unslung and the bullet goes where the sights are pointed, we hit sub MOA targets. But if you want to claim 1/4 MOA accuracy and 1/4 MOA adjustments per positions, I think you have us confused with someone else... they use a bench, special built rifles designed to remove the shooter from the equation, I think they hang out at benchrestcentral.com.

This is why it is important to make the distinction between Tactical Shooting with a Tactical Rifle and shooting Service Rifle with Iron Sights, the places they differ are enough to cause changes, especially with iron sights. But telling a person, their zero will change from the prone to a bench or from sitting to kneeling does not hold true with a tactical rifle. Free recoil versus supported changes, yes, but otherwise, well you see my points.
 
#44
Re: Can zero change 1moa going from bench to prone?

+1 Sterling

Not everyone has logged in the hundreds of hours needed to perfect their solid,stable shooting positions. The rifle will maintain it's zero, but the shooter's position may be all cockeyed. Zero, confirm zero and write everything down to best track what's going on.
 
#45
Re: Can zero change 1moa going from bench to prone?

Samuri,
Then it has nothing to do with the rifle/optic combo changing the POI. Its like i said above, if the shot doesnt go where it should it falls soley on my poor postional shooting. It has nothing to do with the rifle having a different zero as you move postions.
 
#46
Re: Can zero change 1moa going from bench to prone?

OP here...this thing has taken on a life of its own. If I may, I'd like to bring this back down to my newbie level so I can try to fix my problem.

From what I can gather, a 1 moa shift in zero going from bench to prone is clearly my fault. Got it. I know for a fact I don't always get an edge to edge image because I can't get comfortable behind the rifle in the prone position. This is why I was doing load development on the bench.

When I shoot prone my neck hurts, my eyes water, I squint, and my eye seems to lose focus. I think something about my rifle doesn't fit me, but I have no idea how to determine what. I'm 5'9" tall and I'm shooting a 700 in .308 that looks like this:

CIMG2962.jpg


I'm suspicious that the length of pull is long for me because it seems like a reach to get my head in position. I have already moved the scope back 1" from where it is shown in the picture, and that helped.

Worse, I can't seem to get my head vertical enough so I end up looking hard up to see through the scope. I have deep set eyes, so even my eyebrows seem to get in the way.

Please continue your discussion. I'm learning a lot from it. If you don't mind, please also take a minute and try to put me on the right path here.
 
#47
Re: Can zero change 1moa going from bench to prone?

All I know is that in the past few months....I've shot my rifle at a 2/3 steel silhouette target from 500 yards. I've shoot off the roof of my car laying prone across the top.....shot leaning against the trunk using it like a bench.....shot prone on the ground.....and kneeling using a tripod for support...

Hit the steel silhouette in the center mass each time.....the rounds may have moved around a few inches here or there.....but I still put rounds in the center chest of my "suspect" LOL!

Which is all I'm looking for anyway......I'm sure maintaining tiny groups would be different....but how many shots do you get on a "suspect" anyway...?
 
#48
Re: Can zero change 1moa going from bench to prone?

Tim,
Like you said, your LOP is probably to long. Also have you thought about getting some lower rings if its possible? Moving the Karsten cheekpiece up so its not such a fight to get your head vertical and comfortable. The edge to edge sight picture is the most important part, you could be upside down hanging from a tree and as long as you have edge to edge clarity you will be fine (given your able to shoot upside down hanging from a tree). Also if you need to move the scope back some more, can you loosen the rings and slide the scope back towards your face without moving the rings? I cant see the front ring and dont know how much of the tube you have left to play with in front of the elevation knobs but that may be an option.
 
#50
Re: Can zero change 1moa going from bench to prone?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: deadly0311</div><div class="ubbcode-body">Tim,
Like you said, your LOP is probably to long. Also have you thought about getting some lower rings if its possible? Moving the Karsten cheekpiece up so its not such a fight to get your head vertical and comfortable. The edge to edge sight picture is the most important part, you could be upside down hanging from a tree and as long as you have edge to edge clarity you will be fine (given your able to shoot upside down hanging from a tree). Also if you need to move the scope back some more, can you loosen the rings and slide the scope back towards your face without moving the rings? I cant see the front ring and dont know how much of the tube you have left to play with in front of the elevation knobs but that may be an option. </div></div>

From the picture, the base and rings he has are as low as it will go, he will have to change the base to a lower base to do that.

The scope being where it is in relation to the receiver is about as close to the best position it can be to shoot the rifle in all positions, which is with the rear of the scope within that 1/2" of the end of the receiver.

The problem we find with those stocks is the butt plate is too low and when going prone, puts the buttplate almost under the shoulder cup, which causes all the other problems he describes.

Raising his upper body with sandbags, then raising the rear of the rifle up to the shoulder pocket, and getting his head more straight up, and behind the scope, then adjusting the cheek piece to him in this set-up will solve some of the problems, but is a temporary fix.
The cheek piece set that way, will not work in the bench, he will have to drop the cheek piece back down once he gets on the bench.

A stock with a higher but still straight comb would fix some of the problems with the right cheek piece, a too wide cheek piece will cause some of what he describes as well.
Some of my Snipers have this problem with the Karsten cheek piece, too wide and fat, and the original McMillan v-shaped A-5 cheek piece works best for those people.

Some things to think about and try there OP..
 
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