AR Positional POI Shift Test

[Veracity]

I've got 40 rounds loaded for the test. 6ARC
Lapua Grendel necked down
108 eldm
29.4 Lever
2.290 oal
should be 2670-2700 This barrel only has about 40 rounds on it. It is the replacement Rainier UM. If head space grows over these 50 rounds they can stick this barrel up their ass.

VLTOR Fusion F-15 Face trued & shimmed. The VTOR Fusion extension is just as loose as the MUR's
Steel KRG Arca rail
22" +2" gas barrel
Gun weight with Ckyepod & no mag is 15lbs-6oz.

I'm thinking 5 rounds to get a good zero @100y Bi-pod/rear bag & light preload, 5 more to true dope to waterline at 500y with same bi-pod rear bag. Then build and break position 5 x with 3 shots each from prone bipod/rear bag to kneeling off a barricade with a smedium heavy fill up against the magwell.

Does this sound like a reasonable test?
What is the preferred program you guys would suggest I use to calculate mean radius after this test??

500Y on paper will probably hurt my feelings. Hopefully the load will be at or under 1 moa at 100y

Thanks

Test sounds good. I am with @PBWalsh on shooting at 100y. External factors can skew the data at distance. Converting the measurements to MOA/MIL after verifying on paper over multiple groups is what I recommend. Try and shoot them how you normally would from bipod and barricade as to not skew data. If you normally load bipod then do that, however as an instructor I would recommend trying a more neutral position in the future

Hornady 4Dof and BallisticX are what I use for measuring groups. I typically go with Ballistic X as it's only function is to measure so it's quicker to knock out and more refined in my experience.

 

[Paris_Bulks]

The gun still has a gap between the magwell & the rail. For the poi shift flex must be happening across the joint where the extension mates to the upper. Seems like the steel rail may actually aggravate the issue since it's heavy. In addition to the heavy Arca, I've got a few weights out towards the front of the rail.
View attachment 8442357



The range I'll be shooting at for this has 100 & 500 only.
I could just shoot dots @100y, but I'd still want to enter them all into some program to calculate mean radius from dot center for the total group of 15 per position. Not sure what tool/program is best suited to do that?

Your thinking is correct. I've tested positional vertical shift with my LAM through my day scope on a wall at dusk at 200 yards and the shift is greater (.2 mil more) when I have a bipod hanging on the end of the rail.

 

[357Max]

I shot for shift today.

3 rounds prone - 3 rounds bagged tight to magwell x 5 cycles
On the last round prone I shot 1 at small dot upper left, same for bagged, but I dialed U.3 & L.2mil.

There is definite shift, but I certainly had a bit of wobble of the bag. Grip is definitely different between the 2 positions as well. How much if any that contributes I don't know.
This was just a load I picked, not worked up. Shot decent about 1" for 5. I was switching between this test, a 6.5PRC, & a 16" 308 AR letting them cool. It was 96 degrees. 50 rounds each so I was a bit fatigued by the end.

Left the Garmin setup at prone so it picked up all 15 prone + 4 from the bag. SD pretty good for Virgin brass & Lever.

 

[Veracity]

I shot for shift today.

3 rounds prone - 3 rounds bagged tight to magwell x 5 cycles
On the last round prone I shot 1 at small dot upper left, same for bagged, but I dialed U.3 & L.2mil.

There is definite shift, but I certainly had a bit of wobble of the bag. Grip is definitely different between the 2 positions as well. How much if any that contributes I don't know.
This was just a load I picked, not worked up. Shot decent about 1" for 5. I was switching between this test, a 6.5PRC, & a 16" 308 AR letting them cool. It was 96 degrees. 50 rounds each so I was a bit fatigued by the end.

Left the Garmin setup at prone so it picked up all 15 prone + 4 from the bag. SD pretty good for Virgin brass & Lever.

View attachment 8445213
View attachment 8445219


View attachment 8445217
View attachment 8445220

Appreciate the data. Nice work building in the reps of a drill while also doing some testing and load dev.

As far as stability. Kneeling or sitting? If kneeling, double knee down or strong side knee up?

Also, for anyone interested I added the link to my targets. Broken down into .1 mil grids (at 100y) with measurement reference for group measuring apps.

 

[flogxal]

I shot for shift today.

3 rounds prone - 3 rounds bagged tight to magwell x 5 cycles
On the last round prone I shot 1 at small dot upper left, same for bagged, but I dialed U.3 & L.2mil.

There is definite shift, but I certainly had a bit of wobble of the bag. Grip is definitely different between the 2 positions as well. How much if any that contributes I don't know.
This was just a load I picked, not worked up. Shot decent about 1" for 5. I was switching between this test, a 6.5PRC, & a 16" 308 AR letting them cool. It was 96 degrees. 50 rounds each so I was a bit fatigued by the end.

Left the Garmin setup at prone so it picked up all 15 prone + 4 from the bag. SD pretty good for Virgin brass & Lever.

View attachment 8445213
View attachment 8445219


View attachment 8445217
View attachment 8445220

I'd be curious about the loads generated if you moved the sandbag leftward and put the handguard into the L shaped part of the barricade. Bag below, barricade upright stabilizing from Left. Not snugged up to the magwell for depth on the port. More adjacent support, standing position, using that L shape in the barricade. The further out along the handguard's length, the more likely you get diversion. If it's going to flex.

 

[357Max]

I'd be curious about the loads generated if you moved the sandbag leftward and put the handguard into the L shaped part of the barricade. Bag below, barricade upright stabilizing from Left. Not snugged up to the magwell for depth on the port. More adjacent support, standing position, using that L shape in the barricade. The further out along the handguard's length, the more likely you get diversion. If it's going to flex.

Thats not how I normally place the bag. Typically kI’d place it long side under rail with the crease up, that is a little more stable. For this test I wanted to see how well the VLTOR monorail resisted shift.
Maybe next time I’ll shoot it normal and see if shift improves any.
On something like a cattle gate the gun is up to the madwell as I tested though.

 

[j-moose32]

Any chance you have access to a JP SCI-20 to test and see how it does with POI shift? Very curious to how that one would perform compared to the RD15

 

[yinzer_724]

Any chance you have access to a JP SCI-20 to test and see how it does with POI shift? Very curious to how that one would perform compared to the RD15

I'd be curious as well. That's in my list of might buys.

 

[j-moose32]

I'd be curious as well. That's in my list of might buys.

The RD15 price tag puts it in the JP price range. I’ve always seen that if JP is affordable, it’s the answer. Would be very telling to see how it performs

 

[j-moose32]

Tagging @Veracity back in to see if he’s ever put a JP SCI -20 on paper like this

 

[PBWalsh]

Initial range session with a new Aero M4E1 upper with their enhanced handguard and a Blackstone Arms 12.5" barrel shooting AAC 77 OTM. Velocity averaged 2634 with a 16.1 SD. Group shown in the top right is ~.56". Extremely impressed with the upper's performance.

POI shift is now only .2mil and I am very ok with that small of a shift. Looking forward to seeing this barrel develop as the round count increases. Thats half of the shift I experienced with the Vltor/WOA upper. .2mil is within most targets I'll be shooting, and .2mil is easier to add to my data than .4mil.

 

[bigjake83]

Tagging @Veracity back in to see if he’s ever put a JP SCI -20 on paper like this

I have a couple JP SCI-20 that I can perform the above test on. Don't know when I'll be able to get it done but I'd be happy to contribute.

I have two barrel choices for the SCI-20, one in 20" and the other is 22". The SCI-20 Upper is extremely rigid and all barrels are a mandatory thermo fit.

22" CLE Kreiger, CLE Match Chamber, 1-7.7 Twist, Rifle Gas, M110 Contour.

20" Craddock Chrome Moly Bartlein with CLE Match Chamber 1-7.7 Twist, Rifle Gas, M110 Contour.

 

[bigjake83]

Since I also have the JP SCI-20 Large Frame Matching Twin the LRI-20 in 6.5CM I'd be happy perform the same test on a Large Frame.

24" CLE Bartlein, 1-8 Twist, Rifle +2 Gas System, Modified M110 Contour.

 

[j-moose32]

@bigjake83 hell yea, thank you. Very curious to how the JP performs / if the RD outperforms it

 

[AXMC]

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.

Do you have access to a L89 Broadsword upper to perform this same test on?
Thanks

 

[Veracity]

Tagging @Veracity back in to see if he’s ever put a JP SCI -20 on paper like this

Sorry for the hiatus.

Yes I have but only a limited sample. I saw no discernible POI shift. That said I have others say they see about .1MIL.

We all put pressure on guns a little different so take that with a grain of salt.

 

[j-moose32]

Sorry for the hiatus.

Yes I have but only a limited sample. I saw no discernible POI shift. That said I have others say they see about .1MIL.

We all put pressure on guns a little different so take that with a grain of salt.

Thank you. So the JP performs as good or better than the RD15 (and I expect it to considering the price point of JP)

 

[jackinfl]

@Veracity Sir, did you get a chance to document your Seekins Precision uppers? Curious if the IRMT-R upper exhibits the shift.

 

[Veracity]

Thank you. So the JP performs as good or better than the RD15 (and I expect it to considering the price point of JP)

The JP is a solid choice.

You can make about anything have a POI shift with enough force. Doing the testing and putting in the reps to build consistency in fundamentals will aid as much as a new rifle that has no/little shift.

 

[Veracity]

@Veracity Sir, did you get a chance to document your Seekins Precision uppers? Curious if the IRMT-R upper exhibits the shift.

I’ve got a bit of data on them with the average being around .05-.1 MIL with how I shoot them. That’s both large and small frame. The only one I have yet to test is my SP-10M 6 Creed upper.

I’ve been traveling and busy with Army retirement I’ve neglected range time with the AR’s the past few weeks so I apologize for not updating more often.

I’ll get back to more testing as I have a few new uppers/rifles I have been sent to test. I also plan to test various carrier designs and folding adaptors to see if they affect precision.

Edit: Here is a pic I had accessible of prone with bipod then from just a gamechanger below it. (20" 224 Valkyrie)

 

[AXMC]

Since you mentioned a SOLGW m89/l89 upper...any data on them?
Thanks

 

[jackinfl]

Personal data point. last week I took the 5 day Full Sprectrum SPR class at Ridgeline. I learned that my rifle has a ,4mil positional shift low when comparing prone with bipod and rear bag to standing off of a solid barricade with a bag.

My rifle is a BCM Keymod rail with a sawtooth rifles arca rail attached. I have a 18" Bartlein spun up by Craddock Precision with the Allen Engineering AEM5 can.

The facility and instruction at Ridgeline were all FANTASTIC. The instructors demoed everything at exceptional speed and precision with their new Ridgeline LPR rifle. 3 of the 11 students shot the Ridgeline gun. I student bought an upper and one bought a complete rifle during class. Having said that, at no point did the instructors make the class a sales pitch to buy their rifle. I was impressed by this.

My fix for my shift was to just add half of the correction, so .2 up to any of my dope. It seemed to work fine for me. My other thought was to
zero from the standing barricade.

I will defer to @Veracity and his opinion on rather or not that is a fix recommended to others.

I definitely had vertical stringing in prone, as I was trying the Ridgeline, "1 bag to rule them all" philosophy. I am not used to using the game changer in prone and it shows. The shmedium game changer with the heavy fill, on their barricade was super stable for me.

Anyway, I hope this information proves helpful.

Photos show Prone on Left, Barricade on Right then 10 shot barricade group on photo 1. Photo 2 is close up of prone. Photo 3 is close up of barricade. Photo 4 is Rifle on their barricade.

 

[357Max]

Since you mentioned a SOLGW m89/l89 upper...any data on them?
Thanks

Just finished a large frame build with a SOLGW M89HA 16.75" rail. Really liking the rail, it's stout. Will test this for shift in the next couple weeks. This has a titanium barrel nut. Upper is a B-Kings Mod - 0 ( -.004" extension bore).
18" 6.5 Creed, 7.5T, RL + 2" gas.

Receiver face trued & drilled for SOLGW dowel pin. Barrel bedded with 620

 

[JohnDeereGuy1996]

I’d really like to see some people try this with a Lmt mrp. I would assume it would be little to no dispersion?

 

[Veracity]

Since you mentioned a SOLGW m89/l89 upper...any data on them?
Thanks

I no longer have the M89 drive lock 6max and couldn’t find pics when I tested it. But here is one I did today when I mounted a new scope of my M76 broadsword.

 

[AXMC]

Thank you! You don't happen to remember if it did any better? I'd assume the drive lock instead of wedgelock and non-rotation lugs might provide a slight bit of improvement, but not hugely so, right?
Thanks

 

[Veracity]

Thank you! You don't happen to remember if it did any better? I'd assume the drive lock instead of wedgelock and non-rotation lugs might provide a slight bit of improvement, but not hugely so, right?
Thanks

I recall it being in the .15 mil range but I just don’t remember exactly. That was with a 20” and no suppressor.

The drive lock has appeared to help from what I’ve seen on a few students guns. I wish I had more data for you on it.

 

[AXMC]

I recall it being in the .15 mil range but I just don’t remember exactly. That was with a 20” and no suppressor.

The drive lock has appeared to help from what I’ve seen on a few students guns. I wish I had more data for you on it.

Thanks, I appreciate it!
As far as the Broadsword lower, do you like the grip being moved back in relation to the trigger? Do you think it helps you with trigger control?
Thanks

 

[Veracity]

Thanks, I appreciate it!
As far as the Broadsword lower, do you like the grip being moved back in relation to the trigger? Do you think it helps you with trigger control?
Thanks

I do. Having shot a lot of others rifles with adjustable grips to dial in finger placement I prefer it being farther back. For my hand it’s almost perfect with the TLC grip.

 

[sf135]

I no longer have the M89 drive lock 6max and couldn’t find pics when I tested it. But here is one I did today when I mounted a new scope of my M76 broadsword.

View attachment 8485560

Do you have a PDF of these targets? Would love to use them for my range trip tomorrow.

 

[AXMC]

I no longer have the M89 drive lock 6max and couldn’t find pics when I tested it. But here is one I did today when I mounted a new scope of my M76 broadsword.

View attachment 8485560

Did you change anything else besides the scope? If this is the same upper used in the initial test, not only does it seem to prefer AAC OTM's to the Black Hills, but the shift seems to have lessened .1 to .2mil as well.....
Thanks

 

[sf135]

I’d really like to see some people try this with a Lmt mrp. I would assume it would be little to no dispersion?

Veracity said .2 MIL page 1 of this thread. Post 43.

 

[Veracity]

Did you change anything else besides the scope? If this is the same upper used in the initial test, not only does it seem to prefer AAC OTM's to the Black Hills, but the shift seems to have lessened .1 to .2mil as well.....
Thanks

I changed to a much lighter can that is using a 419 adaptor instead of a heavy brake

 

[357Max]

Well This SOB shoots damn good. Only have 50 rounds on it just shaking it out. Will be getting a shift test in the next couple weeks for sure.
Just might shoot this at the Major Land match in Oct.

Factory load of Prime 130 (smk I think). 2617 SD 16.6

First attempt hand load Berger 130 otm pet bolt gun load backed off .8gr
One and done. 2740 SD 7.4

 

[Veracity]

Well This SOB shoots damn good. Only have 50 rounds on it just shaking it out. Will be getting a shift test in the next couple weeks for sure.
Just might shoot this at the Major Land match in Oct.
View attachment 8494081

Factory load of Prime 130 (smk I think). 2617 SD 16.6

View attachment 8494089

First attempt hand load Berger 130 otm pet bolt gun load backed off .8gr
One and done. 2740 SD 7.4
View attachment 8494093

Very very nice!!! Love the KGM can to top it off!

 

[JohnDeereGuy1996]

I found this video interesting. He pretty much claims they didn’t solve poi shift issues

 

[LRRPF52]

Well This SOB shoots damn good. Only have 50 rounds on it just shaking it out. Will be getting a shift test in the next couple weeks for sure.
Just might shoot this at the Major Land match in Oct.
View attachment 8494081

Factory load of Prime 130 (smk I think). 2617 SD 16.6

View attachment 8494089

First attempt hand load Berger 130 otm pet bolt gun load backed off .8gr
One and done. 2740 SD 7.4
View attachment 8494093

You’re running an SCS in that I assume....

I really think 130gr is where it’s at in .260 Rem and 6.5CM gas guns.

My .260 Rem with Berger 130s has been a laser for me, though I don’t shoot it anymore.

The boy has been asking about it, so that will get me to take it out sometime when I get around to it.

 

[LRRPF52]

I found this video interesting. He pretty much claims they didn’t solve poi shift issues

Reading the comments, someone said something about the lower not being ambi because of a patent minefield on ambi bolt catches for ARs. The reviewer stated disappointment in not getting ambi features in an AR-15 in that price range, since the ambi bolt release is very useful in position shooting in matches when on the clock.

I just read through and analyzed the patent diagrams for all the listed ambi bolt catches and didn’t see too much there.

US20100275485A1 *2009-04-302010-11-04 Smith & Wesson Corp. Ambidextrous bolt stop
US20160069628A1 *2012-10-112016-03-10 Heckler & Koch Gmbh. Magazine release apparatus and firearms including such magazine release apparatus
US20210222971A1 *2020-01-212021-07-22 Polaris Capital Llc Bolt catch for firearm
Family To Family Citations
US6634274B12000-12-112003-10-21 Geoffrey Andrew Herring Firearm upper receiver assembly with ammunition belt feeding capability
US7661219B12007-01-102010-02-16 Knights Armament Company. Ambidextrous bolt catch for firearms
US8161861B22009-04-012012-04-24 Magpul Industries Corp. Battery assist device
US8327749B22009-09-102012-12-11 Underwood Joshua A Firearm receiver with ambidextrous functionality
US9291412B1 *2010-03-222016-03-22 Phase 5 Weapon Systems Inc. Monolithic extended bolt release (EBR) devices and methods
US8695477B2 *2010-05-242014-04-15 Tactical Link, Inc. Bolt catch-release lever
US9494378B22010-10-082016-11-15 Lwrc International Llc Ambidextrously operated bolt catch assembly
US8359966B12011-10-212013-01-29 Brotherton William A Ambidextrous rifle bolt stop release
US8978282B2 *2012-08-212015-03-17 Robert Hudson Garrett Lever for ambidextrous magazine releases for firearms
DE102012019422B32012-10-022014-04-03 Heckler & Koch Gmbh Lock catch for a firearm and with this designed handle and weapon housing of a firearm
US9417020B22014-01-102016-08-16 Falkor Sid, Inc.Ambidextrous bolt catch and magazine release and firearm
US9651328B12015-01-062017-05-16 Paul A. Oglesby Ambidextrous bolt release for a lower receiver
US20170241729A1 *2016-02-232017-08-24J & K Ip Assets, LlcBolt Catch for a Rifle

There are several knock-offs of the Magpul BAD, which I’m not a particular fan of. If they work, they’re great, but the mass can induce unwanted bolt hold-opens in some ARs.

One of the biggest issues people encounter, especially when running aluminum GI mags, is that some of the ambi designs out there won’t hold on last round, or rotational inertia on lightweight ARs will inadvertently activate the hold open future when you’re still shooting.

The ADM ambi design avoids this by separating the right side lever from the main bolt catch, separating the masses.

My SilcencerCo Ambi lower has what basically is a PDQ lever. Some have said they had GI mags not initiate LRHO with them.

 

[Veracity]

I found this video interesting. He pretty much claims they didn’t solve poi shift issues

I watched that as well. I’ve shot 4 different RD-15’s and have not noticed the issues that he had. It is hard to say without seeing what someone else sees when shooting to know 100% what’s going on. But he has some valid opinions.

 

[AXMC]

I watched that as well. I’ve shot 4 different RD-15’s and have not noticed the issues that he had. It is hard to say without seeing what someone else sees when shooting to know 100% what’s going on. But he has some valid opinions.

Any anodizing issues on the ones you have/have shot?

 

[Veracity]

Any anodizing issues on the ones you have/have shot?

Not that I’ve seen. I’m not sure how the batches are done or if they have changed who does it.

I have 1500 rounds on mine and used bipod in various position with no abnormal wear.

 

[JohnDeereGuy1996]

Not that I’ve seen. I’m not sure how the batches are done or if they have changed who does it.

I have 1500 rounds on mine and used bipod in various position with no abnormal wear.

Did you get a chance to retest the seekins imrt? How would you say it compares to the ridge line system. If it’s on par I’d say the seekins dmr is a good buy.

 

[-H-]

This is a great thread. In my experience there is going to be a POI shift based on the position of the shooter that varies from a prone zero. This is especially evident with gas guns. How we hold the gun and manage the recoil is going to be different in each position.

At work we do what is called a Variable Height Grouping Drill where we build a shooting position every 7” and shoot a 5 round group. So you’ll shoot at 7”,14”,21”28” etc. This shows two things, whether you have a consistent POI shift, and where your marksmanship fundamentals are at in different positions.

A man far smarter than I explained that when he was deploying to an urban environment, he would zero standing supported off a tripod because that was the position he utilized the most in that terrain. When he deployed to a rural mountainous environment he would zero prone for the same reason.

 

[Dark_Holler]

I also think the Larue Stealth 2.0 upper/rail combo would go well with these other semi-monolithic uppers for comparison.

Also, the rail shift vs actual barrel shift due to torques COULD be different. If you're more worried about LAM or clip-on zero shift, the actual rigidity of the rail system will most likely be more important than lockup to the receiver.

If anyone knows of rail rigidity testing with regards to clip-on or LAM zero shift, please shoot me a link. I think it would be cool to eventually tie both of these together.

 

[JR1200W3]

This is a great thread. In my experience there is going to be a POI shift based on the position of the shooter that varies from a prone zero. This is especially evident with gas guns. How we hold the gun and manage the recoil is going to be different in each position.

At work we do what is called a Variable Height Grouping Drill where we build a shooting position every 7” and shoot a 5 round group. So you’ll shoot at 7”,14”,21”28” etc. This shows two things, whether you have a consistent POI shift, and where your marksmanship fundamentals are at in different positions.

A man far smarter than I explained that when he was deploying to an urban environment, he would zero standing supported off a tripod because that was the position he utilized the most in that terrain. When he deployed to a rural mountainous environment he would zero prone for the same reason.

I agree a lot with this post. I think it's probably impossible to separate shooters positional input from mechanical rail torque when shooting to see shifts. You will see elevational shifts in bolt guns with solid chassis just from rearward grip pressure, or shoulder input, or bipod load. If you're specifically trying to torque on bipod leg or the other you're already biasing your NPOA.

Check out the photo of the M76 positional test. I'm assuming the shooter shot bipod at normal position, brought in close to the magwell, off the bag, and then once more with bipod at normal position. Look at the elevational difference between the two "Far" groups. Not consistent. And the last Far is more consistent with the "Near". So hard to confirm that's all mechanical rail shift.

 

[Thebiglebowski]

Im curious to see test results between SOLGW/Icon defense M89/L89 deflection in comparison to other semi-monolithic.

 

[BurtG]

Seekins upper with a 24" bull bartlein 6 ARC barrel. .2 mil hash marks. Windage was on purpose to separate the groups.

View attachment 8440133

I've not been made aware of an aluminum tube receiver style rifle that doesn't do this to some degree. Some are better than others.

That’s an enhanced upper ?
Edit answered


On another somewhat similar note. Surprising how much flex most firearms have when you add a clip on thermal and want to use Tracir. You can turn on the thermal reticle and see just how much flex there is.


On the original topic , I think most people don’t consider this enough. All enhanced uppers or VLTOR mono for me for precision use.

 

[-H-]

That’s an enhanced upper ?
Edit answered


On another somewhat similar note. Surprising how much flex most firearms have when you add a clip on thermal and want to use Tracir. You can turn on the thermal reticle and see just how much flex there is.


On the original topic , I think most people don’t consider this enough. All enhanced uppers or VLTOR mono for me for precision use.

This is very true. On our work guns I have to make sure guys aren’t loading their bipods when we do the initial co-witness with their IR lasers.

The amount of flex is crazy on non-monolithic types.

 

[BurtG]

Wonder how rigid the mk12s / pri? Handguards are

 

[AXMC]

Wonder how rigid the mk12s / pri? Handguards are

View attachment 8520710

I was just wondering the same thing earlier this morning!
I'm guessing the top rail/riser has to provide a fair amount of rigidity.