Advanced Marksmanship Prone vs Bench zero change

[m1ajunkie]

This weekend I had a chance to shoot in my first precision rifle class. Lots of fun and I learned lots of info.

However, I got out friday to zero my rifle at 100yds off the bench. When I got done shooting, I shot a quick five round group once again to confirm my scope was correct and all was ready for the class.

Well sunday comes and the first group of the day is .3mil low at 100yds. I came up .3mils and all was good the rest of the day. Shooting was done from prone for the entire class, bipod and rear bag.

Is it normal to see a shift in zero like that when going from the bench to prone? Weather conditions were slightly different, but the instructor didn't think weather would cause that big of a shift at 100yds. FWIW, I have seen the same shift in the past with this rifle but using a different NF scope. I thought there was something up with the setup, but the instructor seemed to feel the change in position would cause my shift.

Have any of you seen the same kind of shift when changing position?

 

[Trapshooter12]

Re: Prone vs Bench zero change

Just something to think about. How does your head sit while shooting on the bench vs shooting prone. This may be your answer.

 

[Lowlight]

Re: Prone vs Bench zero change

We did a video on this you can find it on YouTube,

Normal, no, common, yes, it's shooter error.

 

[Greg Langelius *]

Re: Prone vs Bench zero change

When I was shooting N/M Highpower, I noticed a fairly consistent shift in POI wiith each position change.

If I had to pinpoint why, I'd say that the position changes produced at least a subtle shift in my cheekweld, altering the relationship between my eye and the sights.

I wasn't all that into the physics and ergos of shooting then (as much, anyway), and I'd very comfortably agree with LL that it's a shooter-induced issue. As such, it should also be a shooter-correctable issue.

I think less in terms of shooter error than I do in terms of shooter misunderstanding, which can be resolved.

Greg

 

[Lowlight]

Re: Prone vs Bench zero change

Irons are different in you can't take out the parallax and your perspective to the sights is changing.

It's a LOP issue, in that the relationship with you head changes the distance to to the sights.

With a scope, adjusting the parallax is the answer, but if your LOP is wrong you cannot get the proper eye relief, thus changing your view through the optic. Short answer, a scope with a more forgiving eye relief or an adjustment to your LOP.

Mechanically, a zeroed gun is zeroed, end of story. Unless zeroed to the shooters error which is different when poor technique is employed.

 

[Greg Langelius *]

Re: Prone vs Bench zero change

'Zackly...

PS, just noiticed some of the forum rearrangements. I like 'em.

 

[ColtJ]

Re: Prone vs Bench zero change

For what its worth I shot prone for the first time a few weeks ago and the zero did not change, it shot the same as it did on the bench in regards to POI based on sight picture, etc...

 

[Nostradumbass]

Re: Prone vs Bench zero change

I too have had a change in zero "minimal" between positions, but it's cheek weld. Just things I have to work on....

 

[m1ajunkie]

Re: Prone vs Bench zero change

When shooting from the bench, I am obviously more up right behind the rifle than prone. My eye relief didn't seem to be an issue in either position.

Looks like I need to find the video and start practicing to make the poi change go away.

ETA: Is a .3mil shift similar what others are experiencing, or is that more than is normally encountered due to shooter issues?

 

[Lowlight]

Re: Prone vs Bench zero change

.3 mils is a lot... usually not much more than 1/2" you're looking at 3/4"+

<iframe width="640" height="390" src="http://www.youtube.com/embed/Kzg_TgUQEzc" frameborder="0" allowfullscreen></iframe>

There is another one on the YouTube channel, which doesn't change until I actually change my hand position completely, switching to my left hand and floating my thumb, which was all a shooter issue, not a rifle shift.

 

[ColtJ]

Re: Prone vs Bench zero change

Could the height of the scope on the rifle make a difference?

What I mean is if the scope is mounted high it might allow more variance in head/eye position while still getting a decent sight picture. Where as a scope mounted closer to the rifle may not...?

Just wondering...

 

[m1ajunkie]

Re: Prone vs Bench zero change

Lowlight, Thanks for the videos. Looks like I have more dryfire and practice in order.

This is mounted on a .308 ar. It's a NF F1 in badger ultra high rings.

Practicing here at home, it seems like when shooting from the bench my eye is closer to the scope while in the prone position I am a hair further away. The benched position makes me a little more "scruntched" up on the rifle and when I go prone and stretch out my head moves back just a hair, but still within the eye relief.

In the class there was talk about a "cheater button" that is put on the stock to allow you to get the correct eye relief everytime. Looks like I might add one of those to help get the correct eye relief as I am thinking that is what I am doing differently.

 

[bp78]

Re: Prone vs Bench zero change

Is a cheater button a worthwhile training aide to get started in getting a perfect check weld?

 

[m1ajunkie]

Re: Prone vs Bench zero change

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: bp78</div><div class="ubbcode-body">Is a cheater button a worthwhile training aide to get started in getting a perfect check weld? </div></div>

Im not sure because I have never used one, but I see where it could be beneficial.

 

[Sterling Shooter]

Re: Prone vs Bench zero change

I have more zeros than Carter has pills. When shooting an iron sighted rifle in 100 yard reduced course tournaments, comparing corrected zeros from each position, there's typically as much as a 1/2 minute divergence between positions. What it's about is my relationship between the gun and ground being physically different for each position, primarily the butt-to-shoulder and stockweld, but also to some degree the location of my non-firing hand on handguard. Since the rifle recoils differently being held differently, a different point of impact with position change is expected. It's kinda like the result a shooter would get from one position if the position was not re-built properly with consideration for NPA adjustment.

Now, I could certainly take my prone no-wind zero; and, accounting for light, temperature and other, I could shoot standing and sitting with it too. I'd still have a great score, but my X-count would not be as high. Yet, unless a shooter recorded all of his shots in a score book, and was shooting at Master level, I doubt such 1/2 minute divergence between positions could even be discerned for one to come recognize a need to make a sight adjustment. This is because most shooters are triangulating zeros from a very small sampling of shots, each of which are produced with some amount of shooter error. In other words, a shooter would need to have the ability to shoot close to zero displacement to have a benefit from zero refinement with position change. Plus, environmental factors/conditions in any scenario other than competitions may make zero refinement moot.

 

[Greg Langelius *]

Re: Prone vs Bench zero change

I'll review a few concepts from recent topics.

I frequently refer to 'The System", which is my term for the combination of firearm, environment, and their interface, which is the human body. Each contributes in a fundamental way to where the POI appears, each and very shot.

I also suggest that POA and POI are a collaboration. Where the sights and bore point prior to ignition and where they point as the bullet emerges are usually somewhat different locations. They constitute a compensation for the responses of The System. When the shooting position changes, so does The System's response during bore transit; and therefore, so does the required POA.

For some, they have managed to condition their body position so the system responds consistently regardless of position. I think this is what LL refers to when he counsels training as a solution to POI/POA shift according to position.

Whether this is relative either to some form of error, or relates to a certain degree of (mis?)understanding; I think the difference is inconsequential. LL's solution should work perfectly for either definition.

Greg

 

[Sterling Shooter]

Re: Prone vs Bench zero change

Greg,

I'll buy what you're selling. Yet, for something like Service Rifle competition, the solution is not to make the relationship between the gun, ground, and shooter in each position the same because, one, it's physically impossible, since the rifle is placed higher in the pocket formed in the shoulder as the position gets higher, and, two, what's the point when, with an adjustable sight, the sight can be made to accommodate the position. Remember, in this sort of shooting there is no "driving the rifle". Instead, total muscular relaxation is paramount. Now, I'm certain that if I did "drive" my rifle the zero would be the same between positions; yet, scores would be less certain, since making muscle tension consistent shot to shot for a twenty round string of fire, from let's say the standing position, would not be as reliabe as it would be if the position were re-built shot to shot with muscular relaxation in mind. I think muscle is like Jello, I don't want to support the position with it.

 

[Lowlight]

Re: Prone vs Bench zero change

When shooting with scopes, one usually reduces the power when moving from prone to other positions. Moving the power down normally opens up the eye relief so it is more forgiving. This should adjust the scope enough to solve the eye relief issue.

The problem with LOP is most have it too long for positional shooting with a bolt gun. They get it with prone in mind as everything else is an after thought with a precision rifle. So, with some, not adjusting the scope, along with insufficient eye relief causes the problem. I purposely order my stocks shorter with alternate positions in mind.

It's easy to see where an iron sight shooter would have a change, the precision rifle should not. This was written about in the counter sniper manual from the 70's and why Sniper's are encouraged to use scopes and not iron sights. As well another reason they added the parallax to scopes, to fix the cheek weld issue in a combat system. Prone is not always possible.

 

[Greg Langelius *]

Re: Prone vs Bench zero change

Personally, I have never actually mastered the technique that renders my positional zeros identical. Mostly, this is because I nowadays seldom shoot any positions besides prone supported and bench supported.

Possibly in my next lifetime...

Regarding LL's comments on LOP, I think an adjustable LOP/height/cant buttplate could help achieve the identical zero goal.

Greg

 

[Sterling Shooter]

Re: Prone vs Bench zero change

I'd like to see folks, just getting into rifle shooting, shoot irons, as well as with a scope. Here's why, if the beginner, with no marksmanship training, shoots from something like a prone sandbag supported position with a scoped rifle, initially at SR, getting good hits intuitively is quite possible. The shooter may then perceive he has no need for training. Thing is, things will fall apart for this shooter at distances where intuitive no longer works. It's at this point that the shooter may become receptive to some sort of training, yet, he's still lost time, which cannot be recovered. However, if the shooter were given the opportunity to shoot the iron sight gun at SR in the beginning, the shooter would have no doubt about his need for basic marksmanship training, or a scope. Bottom-line, when a new shooter sees an experienced shooter drill a target with irons, a feat which the new shooter cannot possibly duplicate, the new shooter knows there is something to learn; and; usually, this shooter will abandon any illusions he may have about knowing how to do it, to get training right then and there if possible.

BTW, I sell AR's at the gun store where I work part-time in Louisville. Many folks buy the commercial equivalent of the M4 with detachable BDC carry handle sight. I ask these folks if they need some training. The reply is usually,"I don't need any training, since I already know how to shoot". Thing is, these folks will come back to the store later to buy a scope for their "M4", since getting good hits with irons has eluded them. If these folks were to actually get some basic marksmanship training, they'd be able to get good hits with it from irons for most any target/distance, making the expense of the scope unnecessary. I think too many people scope their rifles as a substitute for marksmanship. On the other hand, since scopes or dot sights can indeed help a shooter who knows little about marksmanship, maybe the need for marksmanship training is overrated.

 

[9H_Cracka]

Re: Prone vs Bench zero change

Frank, I'm not sure where you come up with the iron sight shift stuff from.

When shooting irons CORRECTLY with a high degree of repeatability of zeros and POI, one has to be very conscious of sight alignment as well as sight picture relative to the target image.

That, explained in tacticool optical terms, means that we very closely control any head placement "parallax" as a matter of course, regardless of the sighting system (aperture and post, aperture and aperture) and regardless of position.

In my experience, POI shifts occur from position to position based on the pressures placed on the rifle from the specific position. In offhand we are not allowed to use a sling, so the rifle's vertical movement is not dampened by the downward pulling of the front support arm. Shooters often encounter a POI shift in the sitting position due to cant of the rifle and sighting system, particularly with the Service Rifle as the stock is not adjustable. The space guns, with their sights high above the bore, are particularly subject to POI shifts from cant.

Even though standing and sitting are both shot at 200, an elevation correction is often dialed in to account for the differences in the control of muzzle movement sitting versus standing due to the presence of the sling in sitting.

Yes, iron sights shot poorly will act like parallax shift. Iron sights shot well by a skilled shooter, no.

Couple all this with the fact that we cannot run muzzle devices like brakes and suppressors and the whole POI shift from position pressure (mainly standing to sitting) is even more pronounced versus the tactical world.

While I 100% agree with your stance and videos on repeatable POI with the tactical rifle regardless of position as a goal of your training and skills refinement, I cannot agree with your explanation of iron sight shooting and POI shifts due to shooter induced parallax at the mastery level of the sport.

 

[djskit]

Re: Prone vs Bench zero change

I was battling a .3 mil elevation shift for about a year as it was partly an optics failure.

When I was mounting the new scope (same model), I got behind the rifle with no scope and set the scope where I got the proper eye relief - it was one whole slot ahead of where the previous scope had been.

With perfect 20/20 hindsight I realized that my technique had changed over my first year of shooting, but my scope position had not, so it turned out that I was struggling between getting the correct scope relief vs a comfortable position - I was too stubborn to notice the cause/effect.

New scope, new mounting position and a cheater dot on my comb has solved my problem.

 

[Mudcat-NC]

Re: Prone vs Bench zero change

Changes in zero between say offhand, sitting and prone, are quite typical on an iron sighted rifle. Heck, mine even changes between prone rapid and slow prone fire! Now, we are only talking about 1/4 min to an extreme of 1/2 min on days when I really get the rifle in tight for slow fire, but its there. The key is KNOWING its there. I watch guys shoot Xs for sighters all the time and then shoot their rapid fire string and its off a 1/2 min to the right and they cant figure out why or think it was "the wind" that picked up. Wrong...they shot their sighters from a SLIGHTLY different position than their string.

My 200 yard offhand vs sitting zero is quite different due to how I shoulder the rifle and my cant in sitting.

"Mechanically, a zeroed gun is zeroed, end of story. Unless zeroed to the shooters error which is different when poor technique is employed. " - LL

I think I see what you are trying to say here, but with irons (I wont comment on scopes as I dont have enough "real" experience with them to do so) this really isnt true. The "zero" on the rifle is really only a zero for the shooter that put it there. Sure, the relationship between the line of sight of the irons and the center axis of the bore never changes if the sights never move, but thats irrelevant as the irons simply provide an aiming reference and it may or may not actually be at the "center" of the object at which one was aiming when the shot was fired...ie a frame hold, etc. With irons, there are multiple points of reference that have to put back into the proper relationship in order to point the center of the bore to the same spot every time. Otherwise, anyone with a decent hold/trigger squeeze could hammer out great scores on the HP target every time...but, of course, that doesnt happen cept for a few lucky/skilled folks.

And, OP, thats exactly why you see HP shooters with data books or, like what I use, just a simple "zero" book for each of my various hp/lr rifles that I use. Some rifles, like my usual XTC rifle, I know the zeros by memory, but others, I just look in the book, put the sights on and away I go. On most days, they are on the money, on others, maybe not, as there are lots of variables. For a lot of HP shooters, they arent going to notice such shifts as the rounds are still impacting within their hold radius so they may have the same zero every time and never notice a shift or the same wind zero and not notice it was changing from position to position.

I cant tell you how many guys I have coached in team matches that thought they knew their 600 or 8, 9 or 1000 yard no wind zero only to find out during the string that they were off by 1/2 min or lots more!

John

John

 

[Lowlight]

Re: Prone vs Bench zero change

I just went to Byers and shot it and did a video... needless to say I can repeat the issue, and I can eliminate it with a minor change... i will post the video shortly.

Leo, where does the "vertical" come from, equal and opposite reactions, the bullet goes one way, the recoil the other... where is the vertical coming from are you re-writing Newton now ? That is how you handle the rifle, and in this case, it is certainly correctable...

I love the sliding scale that always comes up with Service Rifles guys on here, they are changing so many variables, slings, no slings, standing not standing, sitting and then try to compare it to shooting precision rifle with a scope. It is NOT the same, so the firing task is, but the techniques employed to achieve the end results are not. Just because a Nascar and Tractor Trailer can both get you from point A to point B doesn't mean you drive them the same...

My description of Parallax, admittedly is not correct but it is a way to "show" that you (iron sights) have error in the system that cannot be "dialed" out and is definitely the responsibility of the shooter to align the front and rear sight properly, and any change in that angle of attack on the sights by the shooter will result in a shift. We are not talking MASTER Shooters here, but new or inexperienced shooters who are having this problem.

You're head changes positions so without an adjustment to the cheek piece you are thus moving your eye ever so slightly behind the sights, or scope. This movement is angular as Sterling discusses a lot and causes a shift downrange, which is what is seen by people. You can account for it.

Again, I just did it and shot the video, recoil management is recoil management you either are or you are not... so if you are saying you tend to free recoil more in other positions then that is on the shooter. I don't shoot my precision rifle from the Standing with a sling either, I snap shoot it because if I have to shoot it offhand from the standing shit has gone horribly wrong for me.

I don't know how many times I have to video and show it, but I can certainly repeat it, the shift and eliminating the shift. I have yet to see any of you demonstrate anything, heck not even a single group out of this crowd.

 

[m1ajunkie]

Re: Prone vs Bench zero change

Man this thread has really taken off in the time since I last checked in.

LL I would love to see your most recent video when you get a chance to upload it.

What would be the best way to correct the slight shift I am seeing? Zero prone and focus on that and when moving to the bench try to make my position similar to my prone position?

Since this shift seems to be repeatable for me, I am going to keep the zero I obtained in the class sunday, and use it in an upcoming match in case I can't make the range between now and then. Assuming I am shooting from the same type prone position my zero should be the same correct?

I hate not being confident in my equipment prior to a match, but data from the past 3 range trips confirms the zero shift is repeatable and the exact same everytime. This has me thinking I should be good to go for the match, or is that totally out of line?

 

[djskit]

Re: Prone vs Bench zero change

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: m1ajunkie</div><div class="ubbcode-body">What would be the best way to correct the slight shift I am seeing? </div></div>

Don't shoot off a bench...I'm being snarky and serious at the same time. When I shoot my rifle for "real" it is never off a bench. When I go to the range to test a load or whatever - it is always prone.

The very first time I shot a McMillan A-5 off the bench - I was stringing 5 inches verticle - I settled that down soon enough but eventually swore off the bench - why add a variable that has no practical application?

 

[Lowlight]

Re: Prone vs Bench zero change

Al-righty,

With a SCOPE, and just a SCOPE, I don't care about IRON SIGHTs, that is a niche thing in today's tactical world as very few are using iron sights and the original poster is not using iron sights, so end of story. I get it you have different zero with your iron sights. Of course you do, your stock is fixed your head is changing behind the sights. That is a deviation in the angular attack. Granted I haven't shot irons since the USMC but i was a 5th award expert so I have a minor bit of experience successfully engaging targets with iron sights. But we are not talking about irons here... if you want to talk Service Rifle I suggest you visit servicerifleshootersunite.com because that has nothing at all to do with the original post.

A zeroed gun should be a zeroed gun, period, and I can prove that by demonstrating not only with a precision rifle, but with an M4 with a Reflex Sight on it... the Red Dot of a reflex sight like an Aimpoint does not have to be in the center to hit the target. You can be way up in any corner of the optic and still hit your target because the dot is a parallax free system, <span style="font-style: italic">(mostly parallax free)</span> and the bullet will go where the dot is sitting.

Parallax means the target and reticle are on the same focal plane, so the better your parallax adjustment is, the less deviation you will have if your cheek weld is not consistent or your head is not 100 % behind the optic, as in an Alternate position. You do not need multiple zeroes with a precision scoped rifle because you have an adjustment to dial out the issue that can be seen if you don't. <span style="font-style: italic"> (Refer to red dot sight if you still don't get it)</span> Irons on the other hand, the front sight, the rear sight and the target are on different planes, so you have to line them perfect every-time or you have a shift, different focal planes with no method but placement of the eye to fix it.

Now, changes in how the shooter <span style="font-style: italic">"drives"</span> the rifle through recoil, like with a bipod, can change your impact, but that is a shooter error and not a system error. The rifle is a dumb machine it will do the same thing over and over unless influenced differently by the shooter. If you don't understand the changes and do something inconsistent moving from one position to another you can and most likely will have a change in impact. This is an incorrect result, the correct results is a hit on target regardless of position, as demonstrated by Jacob in the video above -- see positions.

<iframe width="640" height="390" src="http://www.youtube.com/embed/S8-zTfStha4" frameborder="0" allowfullscreen></iframe>

Now, when I moved this morning from the prone, to the bench, I noticed a couple of things:

1st, if just sat behind the rifle, my head was straight up and down, so now my cheek weld was all wrong. I eye relief was different and the height of my eye behind the scope changed. I noticed shadowing at the bottom of the sight picture because my head was higher and I was now seeing the bottom of the scope tube. If you go to your basic marksmanship with a scope you will note that the bullet strike will move in an opposite direction of the shadow. I was looking down into the scope, hence the impact moved up.

2nd shooting from this position, my shoulder were directly over my hips, this is not conducive to driving the rifle correctly and managing the recoil. In the prone the rifle is being driven properly. I am straight behind it, and I am loading the bipod. So, i needed to get forward and get aggressive...

Moving the rifle forward and getting aggressive in my position did a couple of things:

1. It moved my head down to a position better behind the rifle, I no longer had shadowing and I no longer was looking down on the rifle.

2. Pushing my shoulders forward of my hips it gave the rifle something solid to recoil against, so it moved the same as in the prone. I was not essentially free recoiling the rifle which was the case sitting upright.

The results downrange speak for themselves. I was able to repeat the problem and correct the problem. This is something that can be taught, understood and put into practice by any one willing to learn. It's not magic, no voodoo, it is a results oriented if and then proposition. If you do this: then that will happen, if you do that, then this will happen.

 

[9H_Cracka]

Re: Prone vs Bench zero change

LL, if Newton solely ruled the interaction between you, the rifle, the ammo, and the exit of the bullet, then guys like you would be out of a job.

Short barrel time substantially masks many position and execution ills that long barrel time puts the magnifying glass on, but all the factors still exist so one can eff them up with enough effort, even with a light recoiling 3000 fps rifle.

Head position variation affect with irons is directly related to sight radius as well as the size of the objects you are trying to relate. "Minor" is a relative term.

Please re-read the part where I say "I 100% agree with your stance and videos on repeatable POI with the tactical rifle regardless of position as a goal of your training and skills refinement". We have agreement on many things. At the same time though, in areas where your point may be a bit misleading or off, I may share a counter position based on experience, not conjecture, assuming such a thing is allowed around here. If you choose to poo-poo it because it has to do with Service Rifle or wearing a coat, so be it, but being one that is relatively proficient in a variety of disciplines, I would not bring the points into the conversation if I did not believe them to be relevant.

 

[Lowlight]

Re: Prone vs Bench zero change

Leo,

Do you agree, the Shooter's eye, the rear sight, the front sight and the target are not on the same focal plane which is the job of parallax knob to adjust and bring into line... so while <span style="font-style: italic">"parallax"</span> maybe a <span style="text-decoration: underline">minor</span>, misleading statement., however the effects are essentially the same -- or is that too misleading for you.

also I would submit, that with a canted base, you have <span style="font-style: italic">roughly</span> 15 to 20 thousandths of an inch difference between a zero cant and 20MOA cant, at the rear of the scope. So what would a deviation of elevation in the shooters's eye do on iron sights ?

Inquiring minds would like to know ?

 

[9H_Cracka]

Re: Prone vs Bench zero change

I believe the parallel you draw between optical sighting and iron sighting systems via the word parallax is representative for the example you are trying to make. That is not where I took exception Frank. This is:

"It's easy to see where an iron sight shooter would have a change, the precision rifle should not."

Now, you say this in the context of trained Army and Marine snipers under the direction of the best marksmanship coaches, irons, scopes, whatever, in the world.

It is a given that a successful iron sight shooter will carefully hone the skill of putting the sights in correct alignment, regardless of position, before the finger ever approaches breaking the shot. Now, do we have a knob to correct for said errors on irons? NO - but neither did the Corp snipers up until they started shooting the S&B a few years ago.

The skill is the skill is the skill, regardless of sighting system, regardless of position, regardless of whether or not there is an adjustment knob on the scope. Given your appreciation for the root skills that put shots in the center plus your ability to teach them, I hope this makes sense.

And this? "I get it you have different zero with your iron sights. Of course you do, your stock is fixed your head is changing behind the sights."

No, you don't get it. How you align the iron sights is the same, regardless of position, regardless of whether Mudcat has an adjustable stock or I have a fixed A1 or A2 stock.

The only reason my zeroes change at a given distance is thanks to your friend Newton's third law.

"Third law: The mutual forces of action and reaction between two bodies are equal, opposite and collinear. This means that whenever a first body exerts a force F on a second body, the second body exerts a force &#8722;F on the first body. F and &#8722;F are equal in magnitude and opposite in direction. This law is sometimes referred to as the action-reaction law, with F called the "action" and &#8722;F the "reaction". The action and the reaction are simultaneous."

The position changes (can) introduce different forces coming from the mass 1 called the shooter from position to position on the mass 2, the rifle. The action of the rifle recoiling combined with its mass is the constant. The human body, its contact with the rifle, and how it is structured around its contact points with the rifle are the variable.

 

[Lowlight]

Re: Prone vs Bench zero change

the Unertl has a parallax adjustment, you had a spanner wrench and would adjust it in the middle of your adjustment range. The notches in the front, you adjust the objective. As well the parallax deviation is not as great with a 10X scope on the reticle as with scopes of higher magnification. A consistent cheek weld along with a solid zero would correct any angular deviations brought on by parallax.. However when you were issued the rifle you adjusted the parallax for you via the spanner...

And I honestly don't see how you can say, moving your head from prone to standing does't change the angle on the sights, it physically changes the height on which your head sits... maybe you have mistaken your recoil management technique for a problem in the alignment of your eye... I have iron sight here, I can demonstrate if you need the visual. Sure you can change impact with hold but I would submit your head is more the problem. Especially if you are seeing a vertical element to your zero from prone to standing... you can debate that as you do it, but I'll take logic any day of the week and logic says, your head is in a different position behind the sights which are effected angularly.

Guys go so far to blacken the front sight because the light effects how you see the front sight, it's a 3 dimensional object, so light effects. That said, you relationship to your sight has to change just as much to a small degree, why you can't butt change your head position unless you shrug your shoulders.

Again, I am happy to demonstrate on video, i can shoot sitting kneeling standing and you can note the position of my head behind the rifle and see if the height of my eye behind the optic changes or not... I vote yes, it changes, clearly you are voting no...

 

[Mudcat-NC]

Re: Prone vs Bench zero change

I dont argue with LL on issues pertaining to scoped rifles no more than he should argue with 9h, SS, Kraig or me regarding iron sighted rifles. BTW, I hate the service rifle and rarely ever shoot one. And yeah, most of my comp rifles have adjustable stocks, one of the reasons I favor the T2k.

I think some of this thread got mixed up when comparisons were made using scoped rifles vs iron sighted rifles. Two different birds. Oh, and irons arent a niche, btw. Yeah, they may be a whole lot more difficult to master, but if mastered, they can shoot with the same precision, or more, than one can with a scope. I have proved that one more than a few times.

So, if I understand LL correctly, one shouldnt have POI shifts on a rifle with a scope if the shooter changes positions but doesnt change anything else except for "eye position". If thats the case, I can buy that.

Off to find servicerifleshootersunite.com.......

John

 

[Lowlight]

Re: Prone vs Bench zero change

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">I think some of this thread got mixed up when comparisons were made using scoped rifles vs iron sighted rifles. <span style="font-weight: bold">Two different birds.</span></div></div>

This has been my whole point all along... the iron sight shooters coming in and giving iron sight advice to scoped rifle shooters, or even Iron sight sling shooting to people shooting off a bipod.

Make no mistake, I will, can, & have picked up iron sighted rifles and can shoot well with them, not master class well, but definitely hold my own well. My official intro was with iron sights and scored well enough for expert more than once.

Me with Michelle Gallagher shooting her rig in Raton...

By the way I am not giving anyone shooting iron sight advice, not by a long shot, I am simply stating there is a difference.

 

[Sterling Shooter]

Re: Prone vs Bench zero change

Frank,

If I comprehend what you're posting, you're attributing a change in POI with position change to the shooter doing something wrong, or producing an avoidable error; and, if the shooter would do as you do there would be no change in POI with a change in position. Is that right? For example, if you changed position from bipod supported prone to let's say standing unsupported you would expect POI from standing to be the same as it was from prone. In other words, triangulation of each group would reveal the same center or zero.

 

[Lowlight]

Re: Prone vs Bench zero change

Sterling,

Basically Yes.

But at the same time, why would i shoot for precision standing unsupported with the same rifle, if I am standing unsupported I would suspect I have a pretty big target and just want to get the shot off.

Most basic Carbine classes I have been too use an 8" target inside 100 yards.

 

[9H_Cracka]

Re: Prone vs Bench zero change

Yes we can agree to disagree. The issue is not whether my eye will be in the same place on an X-Y plane relative to the rear sight, front sight and target. The issue is what pressures will be acting upon the rifle when my eye is in that position.

I can GUARANTEE you my eye will be in the same X-Y relationship to the other objects, though it may vary some in the Z axis front to back on a Service Rifle due to the lack of adjustability, from position to position, shooting my various position rifles.

The spanner adjustment objective - so what? It is not being used to "fix" a parallax problem shot to shot, and saying that the scope is forgiving does not mean one should/can learn to be lax in their training, which your statement implies to me. Yes I agree and yes I shoot the crap out of fixed objective ST-10s and love them.

Placing your head so you have no parallax, regardless of whether you have a knob on the side of the scope or not, should the goal of all position shooting with the tactical scoped rifle. The stock adjustments, or maybe none at all, most certainly represent a compromise, but the compromise you state to be eye placement X-Y, and I strongly disagree with this. The compromise will be in PRESSURE placed on the rifle by the head, but the X-Y relationship between the eye and the line of sight should not be compromised.

I can do it this way, scope or irons, multiple positions, adjustable or not - the variable is the pressures on the rifle, not the X-Y placement of my eye.

To the extreme end of this we have smallbore prone shooting. If you were to sit down with Eric Uptagrafft or Lones Wigger and talk about this subject, you'd find that their stocks are custom molded/shaped/designed/adjusted so that they can put repeatable pressure on the stock by their head while maintaining the same head position every time they get on the rifle. The spend considerable time honing their technique around PRESSURE, from the head and the rest of their position. They modify their position to control both the amplitude and direction of the muzzle movement, and with the 22, you can see both of these plainly when watching the front site. There is no compromise on their head position X/Y/Z, and no compromise on pressure coming from their head. With Eric able to shoot back-to-back 600s with 70% center shots (that's 84 shots inside 1/2 MOA and 36 inside MOA, sling coat and irons), I think using him as an example of how important pressure is relevant.

You can argue that I and John and Skip vary our X-Y head position from position to position, and you will be wrong, so why not just listen to me when I tell you that we don't?

Shooting the tactical rifle in multiple positions presents many compromises, but your premise that the X-Y head position must vary from position to position is wrong in my book.

The resultant action of the variance in pressure, the POI, is directly related to the barrel time of the projectile along with the amount of energy generated by the rifle (combination of weight, mass being accelerated ((powder + projectile)), and any muzzle device used to mitigate recoil.

 

[Lowlight]

Re: Prone vs Bench zero change

I believe i did go shoot small bore with you and despite the fact it wasn't my game, I don't recall being that far off the mark, so I don't get your point.

What you are saying is, you move the rifle up to maintain the angle on your head, which in turn, change everything about the hold you are using, because the rifle it brought to the eye and the eye is not brought to the rifle, so this compromises the recoil management ability of your shooting. However YOU being a competitive service rifle shooter are not worried about recoil management as much as maintaing a certain form which gives you different results. So, you have the rifle being lifted up to your eye, changing where it sits in your shoulder pocket, essentially this is what you are saying ?

 

[Topstrap]

Re: Prone vs Bench zero change

This has been very interesting, we've dealt with this same thing with our guns although they are very different compared to a rifle they are very similar in regards to what happens when the firing pin hits the primer and starts the projectile down the barrel.

Our barrels are shorter but our velocities are less so I think they equal out that way as to time projectile is still in our barrel as it's being forced to move because of the recoil. Lets say that the scope parallax has been adjusted so when you move your eye around the crosshairs stay perfectly centered. We've found it doesn't affect the POI if we're slightly off center but still have the same grip (position) for you rifle guys)from shot to shot. But if we even slightly change our anything in our setup the POI will change.

Even the slightest difference in how we allow our arm or elbows to touch or hang off the back of a bench affects the POI. I think that the different positions affect POI mainly because you've changed how the gun moves in relation to the mass that is holding (supporting) it and that changes how it moves while that projectile is still in the barrel.

The slight variation in how the gun is supported in various positions changes how it reacts for the milliseconds the bullet is traveling down the barrel so the barrel end is slightly (like in possibly hundreds of thousandths of an inch) but I think it's enough to move the POI slightly from your base position. It seems if you hold the same for each position then that slight variance can be predicted and adjusted for but I'll bet a very advanced shooter can learn to adjust his hold and use the same POA to achieve the same POI in all his positions.

Our long range pistols are very critical of changes in position or grip which I think is the same thing the shooter that shoots in various positions is running into. One of our XPs had a lightweight sporter barrel with no brake and it was much more critical on grip since it tended to rise faster than our heaver braked gun. I believe a heavier barrel with a brake would be less critical on POI change in the various positions change. Then again any fatigue of the shooter and position variations might affect it more during a match than say a lighter barrel. Lots of factors going on here in something that initially seems so simple.

Hope this makes sense, just trying to add something we've learned from trying to make our rigs shoot these long distances. This has been a very interesting topic since it takes the precision of the operator to a higher level to notice these things that affect such small changes in our chase to become better shooters.

Topstrap

 

[Lowlight]

Re: Prone vs Bench zero change

Any basic Google search with the term "Service Rifle" or Camp Perry shows how much they change their position from prone to anything else. In most cases, with their very light recoiling rifles, and weight added, they barely have the toe of the stock touching their shoulder. Its been brought up high to manage the sight picture as there is next to no recoil.

Now, look up the same thing with guys shooting M1s, M1As, etc, they are canting the rifles and putting the butt into the shoulder pocket to manage the recoil. Two difference techniques based on the recoil effects of the rifles.

In these terms there are drastic changes to how you drive the rifles, and will absolutely produce changes in impact.

 

[Sterling Shooter]

Re: Prone vs Bench zero change

Frank,

I trust your technique works. Interestingly, the USAMU's SDM course presents what you would describe as the HP Service Rifle competition technique for standing position with the SDMR, whether the rifle is fitted with a Matech, or an ACOG. Nevertheless, Soldiers are not mandated to use it, or any other presented techniques. If they're getting the job done, even if it appears awkward, they're still left alone. If the Soldier is not getting the job done, a suggestion/demonstration beginning with the statement, "you might want to try this" is used to get the shooter on track, with the realization that techniques are not doctrine, and that what's right for most may not be right for all. The word WRONG therefore is not in the lexicon. That's the problem with telling anyone they're doing it wrong, there's always someone out there who does it right doing it wrong, which only proves the instructor wrong. Have you been there?

 

[Lowlight]

Re: Prone vs Bench zero change

Sterling,

Always and never are not in my lexicon, however as Mudcat has so succinctly put it, not all things translate to other disciplines. So, solutions can present themselves in different forms by different shooters, people will always find ways to adapt to solve a problem.

I have been fortunate enough to attend many outside training courses, as well working with higher Tier groups who also seek outside training beyond anything offered to people In line units. This collaboration helps hone these techniques that clearly diverge from the basics or SDM as well what is seen in service rifle competition. This includes foreign groups that have full time professional Sniper's, and not guys passing through on a way up the ladder.

I am not advocating any competition shooter change their technique or even consider what I am saying. I clearly don't step in places I am not proficient as you won't see me post in the F Class threads or the few service rifle threads. It's not my game.

I do a variety of things I wouldn't advocate to others simply because I have adapted the techniques for my size. It limits several ways I can employ the rifles, but that doesn't mean I can't recognize and correct issues among others.

With Acogs because of the poor eye relief, and with things like armor and helmets I cant the rifle heavily, I bring it to my eye, on an angle, but I also recognize my distance is normally closer, and the rifle is considerably lighter with next to no recoil. Plus usually, the targets are bigger and speed is impressed, so there are a variety of difference that all factor in.

Now with a precision, scoped rifle, it is driven differently even in a run & gun format. The focus is on driving the rifle through recoil to minimize movement allowing me to see the results of my shot downrange regrdless of the position on small targets. Managing the recoil, with a bipod, hard to hard, from alternate positions has proven capable and effective and is used by Soldiers, Sailors, Airmen, and Marines to effectively engage targets across varying conditions. Deviations in zero are eliminated or under poor conditions minimized to the point of being lost in the noise. This allows the shooter to put the focus on the shot and not whether or not their scope needs to be adjusted from the prone to the standing or kneeling. In training I advocate building the position and focusing on getting zero deviation from position to position.

 

[Sterling Shooter]

Re: Prone vs Bench zero change

I've enjoyed this discussion. I respect the learned views of Leo, Frank, Mudcat-NC, and, of course, Greg. If for nothing else, it reveals there's more than one proper way to skin a cat.

 

[Lowlight]

Re: Prone vs Bench zero change

And just something to consider in your travels, looking at this from a combat standpoint, after all we are talking about training war fighters,

The HP competition method compromises the shooter making him more of a target downrange. As well the method of standing as shot in HP blades the shooter exposing under his arms and around his armor. We square up to our targets, presenting our armor as an asset as opposed to blading. I have been to carbine classes that also advocated a straight down double kneeling instead of the angled one knee. Also the HP prone presents more of a target downrange exposing the head to thigh instead of being square reducing the profile.

Small but significant differences. Personally if facing an enemy downrange I would much rather fight your method than mine. Your target is bigger, and vulnerable compared to someone using their armor as an asset presenting a smaller profile. If you add in effective speed rather than looking to build a slung position, you have a very effective fighter. This is very common among outside training courses. Speed and accuracy without being slung is emphasized, the light rifle helps in the case. They manage recoil by extending the support arm to the muzzle, and not tucking it in tight.

 

[Mudcat-NC]

Re: Prone vs Bench zero change

At least from my perspective, high power (I rather use that term than service rifle as HP doesnt always mean SR, as I almost exclusively use a match rifle and for long range, you rarely see a SR out there on the line) really isnt about combat or combat techniques. I think the idea is to develop good fundamentals for shooting, in general, not developing defensive techniques, etc. So talking about offhand shooting outside of cover, etc is, imho, irrelevant. But the skills soldiers or civvies learn while shooting HP certainly translate over to putting good rounds downrange in a fight, if that was ever necessary. I certainly know I wouldnt be standing offhand as I do in a HP match if I was shooting at someone and getting shot at! But I guarantee you that what I learned shooting HP would certainly be a benefit to me in my ability to be effective in that situation. Now, if I wanted to train for that sort of stuff, I would take up a different sport, but I dont see HP as "rambo training", as thats just not what it is. I do see it as precision shooting, cause even though we shoot from slings/irons unsupported, there are some tiny little groups getting shot on a daily basis but us knuckle draggers!

As for other disciplines, I cant comment as I do the same as LL, if its not my balliwick, I stay out of the fray. But at least for HP, I think I know a little bit about it and how to make the rifle put the little bullets where you want them....well, at least on some days I do.

John

 

[j-huskey]

Re: Prone vs Bench zero change

Late to the discussion thanks to vacation and no computer. Once upon a time back in the dark ages, all the Sniper Schools (military) required you to shoot very highly with your prinary iron sighted weapon before applying to SS. If you could not shoot your iron sights, no SS.
Then when you got to the Army side of things, you were issued a rifle with both iron sights and scope. The manual and memory detail that you were required to shoot irons, until the instructors were satisfied you had the fundamentals down well enough to proceed.
Then it was scope balls to the wall the rest of the school and career. IF the Army guy wanted to shoot irons afterwards, he'd TDY to AMU for awhile.
But, and a bigassed BUT, the primary sight was an optic and training on the optic DID NOT go back and forth on iron versus glass.

In this, FRANK is dead fucking on. I am of the school that you SHOULD shoot irons to get the fundamentals down, then when you transition to glass, it is oh so much easier on both you and the instructor.

I teach this way, irons to glass and it still works like it has for a large number of years since glass was introduced to the shooting world.

The high power shooters are correct on all the whys of changing zeros they articulate and most are shooter specific where 30% have the same change in their way of shooting, another 30% have another described manner of change in their shooting, etc, and it is all about position and recoil management not related to "driving" the rifle.

Yesterday, Student and I had a long discussion about something very similar to this, stringing, wide grouping, and a loose bipod stud, causing things to happen when he tried to load the bipod. I took his rifle, zeroed as Frank would say and in any condition, I hit what I shot at AND had sub moa groups. Student did not.
Somewhere in there, I said "Just DRIVE the fucking rifle and quit crutching the bipod, bag, sling, and all that shit." Student has been to Frank and Jacob and understands driving the rifle. Student immediately corrected his head issue and then his zero and mine became identical on his rifle and the problems went away.

When Frank says the change from bench to prone is shooter error of some kind he is correct.
When the HP shooters say the change is due to XX on iron sights they are correct as well.
Each is correct on their chosen topic. Being able to teach BOTH is a blessing to an instructor, because it gets the same point across on ONE day at the range where this has taken two pages.

 

[customshooter]

Re: Prone vs Bench zero change

between the bench and prone or any other psoition, the gun is recoiling at different contact spots and support off your shoulder. This is the primary cause next to different cheek weld, etc...

 

[northern shooter]

Re: Prone vs Bench zero change

Did you try it at extended ranges?