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AR Positional POI Shift Test

#201
itsallbacon said:
Here’s the shooting footage from the above targets

Skip to 7 minutes for the shooting
Click to expand...
For the BCM/Geissele, the only thing I can think of for that insane deviation with the bipod prone shoot was contact with the gas block with maybe the bipod mount back-end hardware. Because it went right back to close POA=POI for the tripod-supported.

Excellent video to illustrate what we’re talking about with positional POI shift though.
 
Last edited:
#204
LRRPF52 said:
For the BCM/Geissele, the only thing I can think of for that insane deviation with the bipod prone shoot was contact with the gas block with maybe the bipod mount back-end hardware. Because it went right back to close POA=POI for the tripod-supported.

Excellent video to illustrate what we’re talking about with positional POI shift though.
Click to expand...
I bet you’re right. I’m going to have to try it again.
 
#206
Tested 3 different bullets out of new barrel today and decided to try this test. Top row is prone, bottom is barricade. Unfortunately not corresponding bullets so I labeled the groups to better match.
B26DDBEF-184D-4018-B1DD-AFC2D335AAC4.jpeg



Mega bullet upper and KAC URX4. I know other people have posted issues with URX4 in this thread but this is my second and I haven’t had issues. I actually have a spare MML upper available but chose the URX4 on standard upper because I can get a lower height over bore with URX4.

I will note on this particular rifle I bridged the upper and handguard with the scope mount. Not intentionally, I just didn’t have a cantilever available and this was unused.

86EBBD2F-5343-419C-A546-494E6C97CE26.jpeg
 
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#207
lennyo3034 said:
Tested 3 different bullets out of new barrel today and decided to try this test. Top row is prone, bottom is barricade. Unfortunately not corresponding bullets so I labeled the groups to better match.
View attachment 8674148


Mega bullet upper and KAC URX4. I know other people have posted issues with URX4 in this thread but this is my second and I haven’t had issues. I actually have a spare MML upper available but chose the URX4 on standard upper because I can get a lower height over bore with URX4.

I will note on this particular rifle I bridged the upper and handguard with the scope mount. Not intentionally, I just didn’t have a cantilever available and this was unused.

View attachment 8674149
Click to expand...
What barrel ?
 
#209
Im kinda battling with this issue right now and im leaning toward it being a fundamentals-consistency issue while shooting my rig from prone with bipod far forward and rear bag. All my groups are around 1”-1.25” and in that group I will have 3-4 rounds stacked in a .5”-.6” group and then a couple shots that blow the group out to a inch or a little more…

Rifle is a vltor Mur upper receiver, PVA Osprey 6 arc barrel, Geissele mk18 rail(bipod attached via arca on the rail), suppressed with TBAC Ultra 7 .264.

I admit I don’t have nearly as much time trying to shoot ar’s at a level of precision like i do my bolt guns and thats why im thinking its definitely me and not the gun or load(i am handloading for this gun). Barrel has right at 200 rounds on it so it should be broke in.
image_cropper_809329B8-ACF5-47D9-815B-818203D25F61-40245-00001F9964AECDEF.jpeg
image_cropper_E3CB7753-F61B-421F-9CD3-517A09F3DC36-34466-00001AFB9FC8AE56.jpeg
This is not always how it shoots but is kind of representative of how i can lay down some great groups and then the next is over an inch. Those smaller dots are right at 3/4”, the grid paper im shooting on is a weird scale.
 
#210
Here's another data point.

Rifle: Cobalt Kinetics CK-Pro with Rainier Match 16" barrel

IMG_5103.jpg


Test (Left to Right)
bipod near muzzle > bipod near magwell > no bipod, shot off bag near magwell

*ignore terrible group sizes, shot cheap practice ammo fairly quickly on these groups

veracitycobalt.jpg


Results:
Appears to be about a 0.2 mrad shift for positional shooting. I probably should have tested this a long time ago. Good to know.
 
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#211
matt33 said:
I definitely need to do more testing, but reading this thread got me curious. I shot my LMT MRP tonight from a bag and also from a bipod extended all the way out on the rail. I did get two nice tight groups, but with a bipod the group dropped .1 mil and shifted .1 mil left.

Barrel is a Bartlein conversion, it's now a very accurate rifle. I went with LMT partially because of the minimal POI shift, along with the ability to change barrels quickly and easily.

I'll test this more this weekend and follow up with some photos
Click to expand...
How do you change barrels easily? I was aware of that feature but was under the impression that you have their own proprietary barrels?
And that wasn't the case for stand-alone handrails/receivers sold separately?
 
#212
vegashelipilot said:
Here's another data point.

Rifle: Cobalt Kinetics CK-Pro with Rainier Match 16" barrel

View attachment 8680139

Test (Left to Right)
bipod near muzzle > bipod near magwell > no bipod, shot off bag near magwell

*ignore terrible group sizes, shot cheap practice ammo fairly quickly on these groups

View attachment 8680140

Results:
Appears to be about a 0.2 mrad shift for positional shooting. I probably should have tested this a long time ago. Good to know.
Click to expand...
itsallbacon said:
I thought making composites to see how these would be expressed as 15 round groups would be interesting.View attachment 8651892View attachment 8651893View attachment 8651894View attachment 8651895View attachment 8651896View attachment 8651897View attachment 8651898View attachment 8651899View attachment 8651900View attachment 8651901View attachment 8651902View attachment 8651904
Click to expand...
Awesome write up! Seriously this rocks. Which SOLGW were you using?
 
#213
tyrider427 said:
How do you change barrels easily? I was aware of that feature but was under the impression that you have their own proprietary barrels?
And that wasn't the case for stand-alone handrails/receivers sold separately?
Click to expand...
I have two different Factory LMT barrels, but a gunsmith named D Wilson can convert virtually any standard AR-15 Barrel to work with the LMT quick change barrel system

I had him convert a 16" Bartlein barrel a few months ago, it is an absolute tack driver now, Factory LMT barrels in 5.56 have been mediocre at best for me in terms of accuracy.

I really like LMT, the monolithic upper rail is my favorite upper on the market, and their Ambi lower is my favorite lower on the market, I just wish they were more accurate as they come from the factory
 
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#214
Seekins SP-10 builders kit. Mullerworks custom 6.5CM barrel. JP guts.

One bag, one tripod, one bipod, one barricade. About a .1mrad from all other positions to tripod and back. And I'm fairly certain it's how I'm driving the gun off the tripod to manage wobble that's causing the shift, not the handguard flexing.
1000007416.png
1000007417.png
 
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#217
lennyo3034 said:
I will note on this particular rifle I bridged the upper and handguard with the scope mount. Not intentionally, I just didn’t have a cantilever available and this was unused.
Click to expand...

I have wondered about bridging my upper/rail with a low YHM riser and seeing if that would help stiffen the system and reduce the POI shift I've seen.

Or if they were still available, something like a Swan Sleeve.

I might mess with that this weekend.
 
#220
black5.3 said:
Im kinda battling with this issue right now and im leaning toward it being a fundamentals-consistency issue while shooting my rig from prone with bipod far forward and rear bag. All my groups are around 1”-1.25” and in that group I will have 3-4 rounds stacked in a .5”-.6” group and then a couple shots that blow the group out to a inch or a little more…

Rifle is a vltor Mur upper receiver, PVA Osprey 6 arc barrel, Geissele mk18 rail(bipod attached via arca on the rail), suppressed with TBAC Ultra 7 .264.

I admit I don’t have nearly as much time trying to shoot ar’s at a level of precision like i do my bolt guns and thats why im thinking its definitely me and not the gun or load(i am handloading for this gun). Barrel has right at 200 rounds on it so it should be broke in. View attachment 8675382View attachment 8675383This is not always how it shoots but is kind of representative of how i can lay down some great groups and then the next is over an inch. Those smaller dots are right at 3/4”, the grid paper im shooting on is a weird scale.
Click to expand...
Nice…I have almost an identical build that I just finished (MUR upper + 18” Osprey 6 ARC barrel + M89 15” Rail). I have yet to shoot it as im still working on some ammo with alpha brass and 107 smk’s.

IMG_3417.jpeg
 
Last edited:
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#221
WeR0206 said:
Nice…I have almost an identical build that I just finished (MUR upper + 18” Osprey 6 ARC barrel + M89 15” Rail). I have yet to shoot it as im still working on some ammo with alpha brass and 107 smk’s.

View attachment 8706494
Click to expand...
Post what kind of results you are getting. I have only heard good things about the M89 rail. One thing i have started doing is incrementally placing the bipod closer to the receivers instead of all the way out toward the muzzle on the rail. I can only image there is more influence on the rail because of the increased leverage on the rail when the bipod is all the way toward the muzzle. I moved it back toward the receivers about 4-5” and noticed a little better consistency. I have much more work to do with my form and shooting gas guns.
 
#222
black5.3 said:
Post what kind of results you are getting. I have only heard good things about the M89 rail. One thing i have started doing is incrementally placing the bipod closer to the receivers instead of all the way out toward the muzzle on the rail. I can only image there is more influence on the rail because of the increased leverage on the rail when the bipod is all the way toward the muzzle. I moved it back toward the receivers about 4-5” and noticed a little better consistency. I have much more work to do with my form and shooting gas guns.
Click to expand...
Im almost done with the ammo so I will prob get to the range within the next few days and will post results. Note this barrel still has to break in so Im not going to scrutinize group size too much yet. I just want the gun to cycle properly during this first trip out 🤞
 
#223
WeR0206 said:
Im almost done with the ammo so I will prob get to the range within the next few days and will post results. Note this barrel still has to break in so Im not going to scrutinize group size too much yet. I just want the gun to cycle properly during this first trip out 🤞
Click to expand...
Good deal, I have about 250-260 rounds on this barrel now so it’s as broke in as much as it will get by now.
 
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