Service rifle shooters have different zeros for standing vs slung. Dudes in the MMS section are asking why they have elevational POI shifts when going from prone to shooting off a barricade with 23lb 6BR bolt guns. How do you know the zero shift is from the handguard flex or from the way you're driving the gun positionally? Especially when we all know ARs are even more hyper sensitive to the way the shooter drives it. Also, you can't post a 5rd group on SH without getting flamed over "sAMPlesiZE!!!" And you're going off big ass'd 3rd groups.
I can do 10 rd groups with this test, I was just following what everyone else did in the thread. I included the 10 rd group just to show what the gun/ammo/shooter combo is capable of. The other POI shifts posted in here are obvious with 3 round groups, so I don't believe it's necessary to burn the ammo. However, I understand what you're saying (I think).
The service rifle zero shift is due to the same as the bipod zero shift.
Correct. The combination of NPOA and forearm flex. Not just forearm flex.
Really? Anticipation with a 23lb gun and 14oz trigger? You just told on yourself. What exactly did he tell on himself about? Dudes currently one of the best precision comp shooters in the world. LolCorrect. The combination of NPOA and forearm flex. Not just forearm flex.
It's from a change in angle of departure. People zero in the prone with a firm rear bag. Then, they shoot from a barricade and there's no solid support under the toe of the stock. The gun moves during recoil and angle of departure changes. POI is high. AB backs this up with a video of a barrel moving rearward during recoil before the bullet leaves the crown.
How do you anticipate with a 14 oz trigger and a 23lb rifle? That's why people shoot light triggers. Anticipating is definitely a thing with pistols. It would be hard to anticipate with a precision competition rifle. You'd have to be a pretty awful shooter. And on top of that, anticipation usually results in low impacts. Anticipation really doesn't make any sense.
I’m not debating the topic. Just here for the comical jab at a dude who is doing the things at a very high level.
The POI shifting up would be the opposite direction of the shift most people see when shooting a free-floated AR15 with conventional barrel nut off a barricade.
I make no claims about anticipation being a factor in any of this. That was the other guy irt bolt guns. I don't know why you feel like you need to clarify this point to me.
It wasn't my intention to come off as combative or put words in your mouth so sorry if that's how it sounded. I think we are talking past each other for a few reasons one of which is that my observed shift is significantly larger than what you're describing at 0.5moa. With a rigid handguard to barrel nut connection like a Geissele or the KAC URX4 I am seeing a downward shift of 0.4mil (tested over repeated 5 round groups) so well over 1moa and significantly outside any expectations of natural dispersion. I think if my shift was under 0.2mils I personally wouldn't worry about it at all.
I threw 1/2 moa out as an example and vague recollections of pics people posted on this thread, but maybe their shift was more.
I zeroed POA = POI with the bipod at 100yd (i.e. no shift condition). When shooting off a barricade + bag with no adjustments to zero, I have a mild downward shift (0.4mils). When shooting mag supported prone with no adjustments to zero I had a significant downward shift (0.8mils) - this isn't something I generally do with this rifle but again only did it to be fair to other shooters without bipods. I only bring it up to demonstrate the point that in my experience, the mechanical POI shift from pressure on the forearm can be orders of magnitude larger than what I would consider a normal NPOA-related shift. The rifle in question has a KAC URX4 and Douglas 16" barrel.
I see.
So if you're forcing hard downward, are you shooting a NPOA? Does POI shift from shooting outside of a NPOA not apply when handguard flex is in question, or is it aggregate?
100% agreed that it was technique induced - I'll give your pointers a try the next time I shoot mag supported prone. It was eye opening to me how much shift can be generated by torqueing on what most consider a "free-floated" handguard. Previously, when shooting the 400pt aggregate with a normal AR I had never noticed any kind of shift because I zeroed the same way I shot the prone position (i.e. mag supported). In the kneeling and sitting strings of fire at 50yd and 75yd the difference in handguard torque also got absorbed into the difference from height-over-bore, so I just learned the holds accordingly.
Yes, that's right. If you mean score it was ugly after I threw away basically 20pts shooting an otherwise okay group into the middle of the lower portion of the 8-ring.
Part of this goes back to zeroing a gun the way you plan to shoot it. If you're going to shoot 90% of your targets, not off a bipod, don't zero off a bipod. You can get away with it a little bit with a 24lb bolt gun that has a rock solid chassis, and a 14oz trigger because so many of those mechanical and positional influences are negated or muted. But even zeroing a heavy precision rifle, I learned a long time ago to stop hard loading bipods legs. I zero neutral or reverse load because it's more similar to shooting off a barricade to tripod. There's extremely few positions where a person is going to be able to load the gun like you would if you were prone digging legs into a 4x4 or dirt divot. Shooting a dot drill positionally is probably a good way to aggregate your zero.
Yup totally agreed and I tell everyone I know that if they aren't keeping a bipod on their AR15, don't zero off one. I also don't recommend using a bag to support the handguard at the front when zeroing prone for the same reason. If they use a bag for support to zero, I tell them to put it as close to the magwell as possible.
Inconsistent NPOA changes the pressures to the hand guard, which induces the POI shift (just like the bipod/barricade movement)Correct. The combination of NPOA and forearm flex. Not just forearm flex.
It's from a change in angle of departure. People zero in the prone with a firm rear bag. Then, they shoot from a barricade and there's no solid support under the toe of the stock. The gun moves during recoil and angle of departure changes. POI is high. AB backs this up with a video of a barrel moving rearward during recoil before the bullet leaves the crown.
I'm not calling it random things. You said anticipation. Legitimate question: Why do we call it anticipation? What are shooters anticipating? And what do they do when they anticipate. They're anticipating recoil. By flinching. They're usually trying to counteract recoil. This means the majority of the time they're pushing back into the gun. Which usually results in a downward movement of the muzzle...over a point of fulcrum.
Recoil pushing a gun the way I'm describing isn't really debatable is it? I mean it's why muzzle brakes are made the way they are, right? What I'm describing is all very logical isn't it? In any other conversation it wouldn't even be insightful, much less going against the grain.
I'm honestly not sure what you're trying to to argue or prove. I even mentioned what you said could be a culprit. I also never claimed that there's only one thing causing POI to go high, I just stated what I've seen as the most common issue I've seen.
Here's what I'm trying to argue.
I don't disagree with most of that. With the caveat that I see as much low POI with bolt that I see high from shooters. And also see no discernable difference in various positions from some high level shooters I know.
That last paragraph sounds like it was written by my ex wife. Just seeping with resentment.
I'm just kidding, lol. I've never been divorced. But seriously, I see what you did there.
Well I'm also dead tired and probably grumpy so don't take it personally. LolThat last paragraph sounds like it was written by my ex wife. Just seeping with resentment.
I don't wonder because I understand it and I know what shooter inputs do to maintaining a zero. I firmly believe, and I'm not lecturing you because I know you have a long background in institutional instructorship, that the first achievement of shooting isn't necessarily learning how to place rounds in an X ring. It's understanding the fundamentals enough to be able to continue to coach and train yourself. Knowing the fundamentals of MMS well enough to troubleshoot your misses is an invaluable skill. And I also believe a lot of PRS shooters learn how to shoot without any institutional and professional instruction. They lack a common language and core. I also believe being able to shoot your zero is one.of the list underrated skills. Your data is anchored from your zero so beyond your ability to account for environmental factors in your data at distance, it all matters not when you can't shoot the same zero from position to position.
I think a lot of people are going to see your posts and what they take away is "it's all handguard flex". You know how it goes. 100%.of the information is taught. 80% is understood. 60 % is retained. And only 50% can be articulated. So real key points have to be emphasized.
I totally agree about paper. I was the PI for Advanced Rifle Marksmanship at the course I instructed at Bragg. Shortly after I left they got rid of ARM. The next portion of the course was sniper marksmanship but the $5 million dollar automated range system they had went down so they distilled it from shooting snaps and movers, deliberates on paper to shooting two rounds on steel at known distance. Basically Field Shoot but with ranges provided. Within a year they had lost any sort of fundamental rifle marksmanship proofed by shot group analysis. Later, I was a Master Trainer for a groups sniper program. All my instructors were the product of this new course. They taught truing the ballistic computer day one on the range. On a truing bar. When I came aboard I asked them if we should reinstitute shooting groups on paper targets in the pits for the first week of range time. They all agreed no. It was antiquated. I then set up an instructor training event with the AMU service rifle team and took them to Benning to learn ARM from service rifle shooters. Because they never learned it at Sniper school. We shot 20rd groups on paper targets on lifters and my instructors were wow'd. The same guys that said it was antiquated but had also never done it, were now singing it's praises. When we returned we decided not to true the students ballistic computers until the end of the first week. My reasoning was new shooters won't shoot the same zero day to day. They are learning and changing the way they are driving the gun as they are learning. So any true they think they're getting is flawed by their shitty zero. We switched to gathering data for the first week along with DA and at the end of the first week we sat down and examined their weeks data and trued based on the aggregate.
Service Rifle is a big reason I do so much on paper. Chalk it up to almost a decade at AMU and having the ability to do it almost anytime helped with the obsession. It is unfortunate that emphasis on such things have almost gone away. With the Corps changing its program drastically and snipers going all to R&S, I can only hope the Army keeps its program and continues to progress.
Looks like there might be an anti-rotation projection on the handguard...does it fit into a notch on the upper? Is that what you're talking about, or are you referencing the long barrel nut?
I think the 6 arc maritime rifle or whatver is differnt. But you can’t get that
Are the two bipod far groups the same setup? I often wonder, as someone who has chased zeroes how much body position shift plays into the results of the tests. If I did this with a large frame gaser and was out of practice, my results might not be consistent.
If you're referring to the Aero Enhanced groups, yes. Exact same. I had three rounds left after shooting the 4 x 5rd positions. At that point the gun and suppressor was hot. I was surprised at the POI on that last three round far bipod group on the right side of the target. I plan on shooting a variation that is far bipod, bag, far bipod, bag, far bipod to see how repeatability looks. You can draw your own conclusions about the rail defection vs my ability to shoot the same zero. I would also say this 22 ARC has been a little confounding and not as consistent as a straight 223.
