AR Positional POI Shift Test

#101
I recently did a test with my factory 18” Seekins DMR. Note my zero in the bottom right target is high, and correlates to the “bipod far” square, which makes sense because that how I zeroed the rifle.

Very pleased with the results of the Seekins. ~0.17 mils of shift is well within acceptable when accounting for my performance with this ammo.

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#102
JR1200W3 said:
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.
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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).
 
#103
JR1200W3 said:
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.
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The service rifle zero shift is due to the same as the bipod zero shift.

For bolt gun shifts in my experience it's often shooter anticipation from the barricade.
 
#104
JR1200W3 said:
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.

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.
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What exactly did he tell on himself about? Dudes currently one of the best precision comp shooters in the world. Lol
 
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#105
I'm wondering if anyone had done any testing with a Radian.

Mine is still quite new to me with only about 200 rounds through it. I've been extremely impressed. I'll try to get some testing done but no promises on when. I'm a busy guy right now with very little time to shoot at coyotes, let alone some tests I had never considered!

I also have a Wilson Combat that is essentially unfired. I think I put 20 rounds through it for a function test.

I'm sure that all of my "lessor" AR's will have significant impact shifts if I look for it. And I will. Eventually.

Man....I learn so much on this forum.

EDIT: AR's are definitely not new to me, I bought a Colt SP1 in 1981, but I'm a bolt action aficionado. I shoot far more rounds through the bolts than the semi's.
 
#106
JR1200W3 said:
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.

It's easy man. Free recoil a rifle off a bag and watch the POI shift up.
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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.
 
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#107
JR1200W3 said:
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.

It's easy man. Free recoil a rifle off a bag and watch the POI shift up.
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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.

If you are saying "how do you know it's not you?":
1. Shoot modified prone or prone with bipod attached at different points on the handguard to see if the change in leverage on the forearm changes your results.
2. Shoot a monolithic or semi-monolithic upper side by side with a regular AR and watch the shift get cut in half or better.
 
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#108
JR1200W3 said:
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.

Look, I'm on this journey with you guys. I know handguard flex is a factor. I went from a DD MFR 15 on a 22ARC to an Aero M4 Enhanced, and just bought a RD LPR 15 that I'll probably knock the 16" proof barrel out of and put a higher quality custom barrel in it. I just think it's a little naive to think you can fully isolate the handguard flex. In a practical sense it doesn't matter if it's handguard flex or you driving the gun a certain way, or the two intertwined. If it's consistent and evident then you have to know what it is and factor it in when shooting from different positions and barricades. I with you all up to there. Where I differ is the idea that you can fully isolate it to the handguard. We all know ARs are hyper sensitive to shooter inputs and demand so much more of you. But then people want to shoot 1.25" 3rd groups from different positions and assume that the POI difference in the 2rds that landed close together (but not the third that landed in the original POI) is all handguard and not the gun responding to a different positional input from the shooter. I mean, we know that you can record higher MVs shooting in the prone than sitting off a bench where the shooter doesn't have the full 6ft of his frame grounded to push back against recoil. But somehow we think we can isolate all the other noise and attribute everything we're seeing to handguard flex. I also "think" that you're going to see more flex with the bipod on the end of the handguard, especially shooting in the prone depending on how much you load the bipod legs. I've seen people claim they can feel chassis foreend flex on heavy bolt gun chassis. (I'm pretty skeptical of that too, I think they're seeing flex from the bipod legs and attachment). But it's an example that it's where you're going to flex the handguard the most. Shooting off a bag with the magwell pushed forward against it or off a tripod isn't going to have the mechanical advantage to flex the forend. So if you want to really test flex, I think you should be shooting long bipod. Of course if your goal is to identify the practical zero shift from different positions, sure, keep shooting the positional test you're doing now to best reflect what you're going to shoot in a comp.
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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.

One other observation is that after zeroing off bipod, I shot a 10 round group prone mag supported (part of a friendly competition and didn't use bipod out of fairness to shooters without one) and found a 0.8mil (!!!) downward shift. I think this makes sense because in mag supported prone I am applying additional downward pressure on the handguard to counter balance my cheek pressure on the stock. This is completely opposite to bipod supported where the bipod is applying upwards force, and it logically makes sense that the shift is larger than the shift I get off a bag and barricade because that is a relatively neutral position with regards to handguard force.
 
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#109
JR1200W3 said:
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 had to read your description three times. Still not sure I understand it. So to back brief: When you zero from a bipod your POI has a downward shift? And then when you shoot prone, mag supported you have double the downward shift? And then articulate that the handguard pressures are opposing between bipod supported(up) and mag supported with your support hand applying a heavy downward force?

Random question: zeroing with a bipod, downward shift. Shift from what? Did you already have a zero from a different position? And the downward shift was from a known good zero, but just from a different position?

As a complete aside to handguard flex, shooting mag supported in the prone is a really great tool for teaching NPOA(Natural Point of Aim). I developed an ARM (Advanced Rifle Marksmanship) POI based on the 400pt Rifle Aggregate. We had Tiger Swan come out to our unit as part of a PMT for an Afghanistan rotation. Their pistol instruction was on point and their rifle instruction was okay, but the 400pt Rifle Aggregate they used to teach their version of the rifle fundamentals is a great drill, although it could be pared down to a 300pt drill. You shoot 3 x 10rd, time fire strings on an IPSC target and your looking for A zone hits. From three different positions/ distances. 100m Kneeling, 200m Sitting, 300m Prone. The drill starts Standing, low ready, in kit, and you have 60 secs to go kneeling, fire 10rds with a mag change anywhere you want in the string. Move back to 200, Standing to sitting, 60secs, 10rds, one mag change, 300, Standing to prone, 10rds 1 mag change. Walk up and score all 30 shots for a total of 300pts. You can apply different scoring depending on the target you're using. B8 repair center, FBI Silhouette, etc.

When I teach shooting in the prone in kit, mag supported, you have 4 different axis that your barrel can try to point. Up, down, left and right. Place the mag and point the barrel,.if your too high on target you have to readjust the buttstock in your shoulder slightly up to adjust elevation. For left or right you pick up the gun and place the mag so the gun is pointing directly at the target, on sights so you don't have to move your body to get on target. And you do all this with your firing hand. You don't apply your support hand until you have a good NPOA. Once you do, you LIGHTLY apply your support hand as far out in the fore end as possible with your elbow providing support off the ground. The role of the support hand is to steady the long axis of the rifle only. If you're using your support hand to point the gun on target you're not shooting a NPOA. It's just there to quell the normal wobble zone with light guidance. Your body should aim the rifle naturally in target. Your firing hand pulls back into your shoulder and cheek pressure helps lock the gun in.

I use a VTAC sling to wrap in the kneeling and sitting. This allows the gun to rest in a position, in a NPOA. When you can shoot over 275 on a B8 repair center on this drill you're doing pretty good. And you're generally all inside the black. And as I think about it, the last time I shot it, I didn't have an obvious 10rd POI shift from, say sitting slung vs prone. You might want to try using your support hand as light pressure to steady and using your firing hand to provide the majority of pressure.
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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.

The drill I was shooting actually was the 400pt aggregate shot on a B8 repair center with no mag change. I also do not have an obvious POI shift going from kneeling to sitting but I did going to prone - to your point it is technique induced due to the amount of downward pressure I was applying to the handguard, which did not feel like an extreme amount. I did shoot another group mag supported prone to confirm and both times I was impacting about a half inch below the bottom edge of the 9-ring (i.e. ~3moa shift).
 
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#110
JR1200W3 said:
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?

I have no doubt the gross amount of POI shift you saw was at least partially due to handguard flex if not a very large portion of it. Again, I'm not a flat-earther. But even in your example when you admit to applying pressure with your support hand a person has to wonder what mix of positional influence and handguard flex is the sum total result. I guess in your defense, if NPOA violation was the cause of the shift it would be the gun trying to return to its NPOA which would be up(if you're forcing down) so it would result in a shift up. Should probably stop torquing on the handguard.

And funny coincidence that we're both familiar with this drill.
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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.
 
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#112
JR1200W3 said:
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.
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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.
 
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#113
JR1200W3 said:
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.

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.
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Inconsistent NPOA changes the pressures to the hand guard, which induces the POI shift (just like the bipod/barricade movement)

As far as the anticipation.. I spoke to what I have seen, over hundreds of shooters in recent years from barricades. Brake flinch, anticipation, trigger freeze and whatever else you would like to call certain phenomenon. Not everyone has a 23lb gun and a 14oz trigger. There are some theories of longer barrels with slower cartridges (ie 308) that the departure angle changes while the bullet is still moving through the bore which could be causing a higher impact. Sometimes it’s just where the reticle was when the gun moved and others it could just be a mix of things.

I am here to share my experiences and knowledge so if that is me telling on myself then cool. Feel free to come visit sometime and show me how it’s done.
 
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#114
JR1200W3 said:
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.

When the gun has a bipod way out front the two points of contact with a solid surface is the bipod way out front and a rear bag. Much harder for recoil to push the barrel back and up, like it naturally wants to do. But when the fulcrum is a single point of contact, like resting on a bag over the center of balance, it's much easier for recoil to push the bag back and up. A natural movement of recoil.

I challenge anyone reading this to free recoil any gun they have off a bag in a barricade with the mag well pushed up against the barricade and see where the POI goes.

When I get home, I'll shoot a 18lb 6BR bolt gun in an ATX chassis long bipod and short bipod and see if POI changes with any consistency to what you're seeing with your gas gun.
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Look forward to your results. Make sure to post triggercam footage too
 
#115
JR1200W3 said:
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.

Would you not agree?
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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.
 
#116
JR1200W3 said:
Here's what I'm trying to argue.

Having a higher POI when shooting a position like bagged barricade or close bipod is a natural cause of recoil, whether you're shooting a bolt gun or gas gun. So It makes a ton of sense that a POI shift will exist between prone and bagged barricade without even getting into the factor of handguard flex. In a heavy bolt gun with a light trigger it can be pretty easily managed by a decent shooter. However, if a shooter is free recoiling a little more than they'd like to admit, they can see a upwards shift of POI. Which you said was a result of anticipation. I am also arguing that anticipating usually results in low shots. And that all this points to POI shift being more a ratio shooters input and handguard flex, than only handguard flex. So when you post your zero offsets it isn't necessarily just the handguard.
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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.

My entire point of making the target and the post was to make people aware of the shift that can be caused due to the design of the AR platform. Never stayed there were not other factors influencing shifts. However one should test and test again and not just accept a few shots as their absolute POI shift.

I don't know about you but I'm confident in my abilities to shoot from various positions and determine what my POI shift is without wondering if it's because of anticipation or fundamental issues.
 
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#117
JR1200W3 said:
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.

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.
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Well I'm also dead tired and probably grumpy so don't take it personally. Lol


I 100% agree and harp on zero, zero offset, and massive amounts of 100y/m work in my courses. I've had some students taken back when they hear how much work we are going to put in on paper at short distances. Then after a few days they understand and appreciate the foundation and understanding they have built by tirelessly working their positions on paper. Paper doesn't lie is something an old USMC Teams shooter from the 70's told me about a decade ago and I've truly taken that to heart.

NPA and Zero are so overlooked in my experience from other shooters and instructors. I am not sure if it's due to students wanting to do the fun and sexy stuff like going immediately to 1000+ yards or if it's just lack of knowledge on the instructor. But whatever it is, it's unfortunately leading the student astray and sometimes I feel the teacher needs to be like Steve Jobs and give students what they need versus what they "want".
 
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#118
JR1200W3 said:
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.
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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.
 
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#123
Unless they've changed something that's just the regular barrel nut for the Geissele handguard - it's not semi-monolithic and you still torque it onto the receiver same as most FF handguards. I would expect to see POI shift switching between barricade and bipod using this.
 
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#124
Eyesquared said:
Unless they've changed something that's just the regular barrel nut for the Geissele handguard - it's not semi-monolithic and you still torque it onto the receiver same as most FF handguards. I would expect to see POI shift switching between barricade and bipod using this.
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I think the 6 arc maritime rifle or whatver is differnt. But you can’t get that
 
#128
mr.awaka said:
I’m wondering the same thing. @Veracity were you able to test one of these?
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They are very rigid, I'm not sure if they are still offering the Steel Barrel Nuts and collar but I would torque the barrel nut and collar down to 70 ft lb, and once you top it off with the top rail it's locked in.

When working with the PRI parts make sure you have the proper tools they offer for the Barrel Nut and Collar.

On a side note, I know it's not clone correct but I always used the unmarked Vltor Upper Receivers for increased rigidity.
 
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#129
This is a great thread - thanks for starting it and for your data to kick it off! I have noticed different levels of POI shift between 7 different ARs. I have noticed it is less for rifles with stiffer connection between receiver and hand guard and thicker barrel contours, but I have never quantified the shifts. Generally the shift doesn't seem to be worth thinking about in the heavy barrel AR10s (less with SP10 than a custom with Aero M5 upper, almost zero for Armalite T10 with true free-float barrel). The shift seems to be a few tenths mil for SPR/DMR AR15s with medium contours (White Oak SDM upper/PWS lower and Seekins DMR) but is much larger, maybe close to 0.5 to 0.7 for the lighter contour AR15s with light weight hand rails (e.g. DDM4V7). After reading this thread I am going to try two things - be more consistent with down-force when in a position that requires it, and quantify the shifts for each rifle in each position.
 
#132
JR1200W3 said:
RD LPR-15 with a 20" WOA barrel. MK262 77gr. 100yds
View attachment 8564260

Self-diagnosing, in the prone I'm shooting a light grip, neutral bipod load, about as medium shoulder pressure I can but I was shooting off a polished, glazed concrete floor with a CkyePod's clawed feet so the gun slides forward. Off the kneeling bag, I'm putting a lot more shoulder into it and the gun is much more fixed with my support hand c-clamping the handguard against the bag. I shot tripod twice. Locked the leveling head the first time and unlocked it the second time to essentially free-gun it. Hence why the POI resembles the bagged group. I wasn't surprised to see a POI shift high off the locked tripod but I I was surprised at the windage shift too. I think the difference shown between the two tripod shooting styles shows just how much influence support hand placement and shoulder input has to NPOA and POI.

ETA: Aero M4 Enhanced in 22ARC. 20" Craddock RTR. Berger 85.5 Hybrids, 28gr TAC, 2818fps, 9fps SD over 20rds.

View attachment 8572389
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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.

That being said, I witnessed first hand the difference in moving groups vertically down with an SP10 when I strapped on a lightweight bag in front of the magwell vs resting on a game changer off barricades.
 
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#133
JR1200W3 said:
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 POInon that last three round far bipod. 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.
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Sorry, wasn't trying to call out your groups. Just get some more info so I can understand the test. I wasn't sure if the last group with the bipod far had another variable at play as well. Do you think the rail design drove more of the flex in that upper?

Have you found mirage moves groups in a certain way? I feel like I have noticed it drifts them up slightly.

I wish I had run this test with an old Geissele rail I was running with a Douglas barrel.
 
#134
Veracity said:
Yes. That’s how semi-monolithic are designed. LaRue, Aero Enhanced, Seekins, Ridgeline, Mega all have models with similar setups. The added receiver thickness helps as well.

I’ll try and mount an LA5 this week and see what I can do for rail deflection. I’ve never seen a rail that did not have some movement so I doubt we will ever get to 0, but some have flexed less than others. The most rigid I’ve seen so far is the SOLGW M89/L89 rails.
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I know the SOLGW M89/L89 wasn’t part of this initial test, but do you recall what kind of shift you saw with those? I imagine it’d be less than the M76 you tested.
 
#135
JR1200W3 said:
I didn't take it that way. I'm curious about that last group as well. I'll shoot it again tomorrow.

I think I'd have a hard time making a conclusive call from just that 20rds but it is obvious that there's a POI change. I think it warrants experimenting shooting bagged and tripod with a few different techniques. And shooting a dot drill.

However, I do feel the LPR is in another league when it comes to handguard rigidity. I'm starting to think the Aero Enhanced is a half step. We might find out in the future that barrel nut torsion is not as much of a factor as handguard flex is in conjunction with how we drive the gun. Like it's less about mechanical flex on the barrel and more about handguard flex influencing our shooter input in our zeros. If that makes sense....

I think I'm going to buy another LPR, stick a custom 22 ARC barrel in it, and cut out the top of the handguard to allow a .936" +2 adjustable gas block.
Click to expand...
How hard was swapping the gas block when you did the barrel swap?

I totally agree that there is something going on here. If it's happening with the Enhanced and LPR, it can only be worse with standard handguards.

I need to do this test with clipping into arca on the tripod. Particularly with my SP10.
 
#136
JR1200W3 said:
The LPR gas block comes off pretty easily. It's just a large jam nut. It wasn't loctited or anything. Just torqued on. As far as putting a new barrel in and installing a new gas block in it...the same as any thermally fitted AR barrel. I ended up thermally fitting a gas block on the replacement barrel as well. It's solid AF. Not going anywhere. The set screws are basically there for moral support.

This video demonstrates how to remove thermally fitted barrels and install them. If he makes it look easy, it's because it is. I've had brake jobs more complicated.
Click to expand...


Did you get an oversized gas block area on the new barrel for the thermal fit?

I just popped a 300Blk barrel in a BCM thermo fit upper. I unashamedly put the front of the upper into my wood stove. It was just a low level of coals and I was able to control the upper with a heat proof glove to make sure the front end warmed up. Barrel popped right in. Cooled down and it was snug as a rug, no way it was coming out with a dowel and serious hammering.
 
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#138
TxAg93 said:
I know the SOLGW M89/L89 wasn’t part of this initial test, but do you recall what kind of shift you saw with those? I imagine it’d be less than the M76 you tested.
Click to expand...
I have a new 14.5" L89 Broadsword I will be testing this week. I had a L89 20" in 6Max previously and I did see less shift than the M76, but it was tested only a few times.
 
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#140
Did a POI shift test with a Cobalt Kinetics upper today. 16” Sons SPR barrel with the longest cobalt rail and the Annex Defense XL Arca rail. The bipod far position was at the end of the arca which places the bipod under the gas block (midlength). Overall I’m happy with it, the can is a Hux Flow556k for reference
 

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#142
Alright it’s been a while since I’ve been on the hide but I was googling about this stuff and saw myself so I figured I’d jump in.

My video was posted as evidence regarding the shift in the LPR. I kind of went down a rabbit hole on this lately and my only conclusion is that I don’t know.

I was seeing a repeatable .2 but I was inducing it by changing the amount I was loading the bipod. I’m starting to think it’s a symptom of changes in my shooting, not handguard/ upper flex. Further evidence came when I re-created the same .2 with an LMT. FWIW I did post another video to roll back some of my assumptions which I now suspect may be wrong.

Thanks for all the posts in here, this is all pretty interesting and you’ve collected a lot of good data.
 
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#143
I've done some testing of this myself. if you start loading bipods or vertical grips, you'll start seeing significant shifts depending on the barrel nut design. but to compare i've tried to have a completely neutral load on the rifle.

I have currently tested the MR308A3-28, and the mr223a3 with geissele handguard.
I cant discern a significant shift with the fiocchi 55gr ammo im using in the mr223, anything gets lost in the dispersion. need some better ammo first.

for the mr308 i got the groups below, shot at 200m to see any shift a little better. so you are looking at about 2" at 200m with only the weight of the rifle loading the handguard.

mr308 shift.jpg

1737471629769.png
 
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#148
I'm also curious why they would notch the top rail at the upper to handrail transition...unless it's part of how the barrel nut is torqued, it seems like an unnecessary weak spot.
 
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