AR Positional POI Shift Test

[NHPiper]

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.

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.

 

[JR1200W3]

Sorry, wasn't trying to call out your groups.

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.

 

[TxAg93]

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.

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.

 

[NHPiper]

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.

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.

 

[JR1200W3]

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.

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.

 

[NHPiper]

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.

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.

 

[JR1200W3]

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.

White Oak Armament barrels have slightly oversized gas block journals. I used a Black River Tactical low profile fixed gas block and the combination of the two required some polishing with a high grit sandpaper and heating of the gas block.

If you want an infallible gas block arrangement, I don't think it gets better than that. As much as I like the RD gas block design, I don't think it's more secure than what I ended up doing with the WOA/ BRT gas block. There's zero gas escaping from it after 100 + rounds. With a standard rifle length gas tube on the 20" WOA SDM barrel it's slightly over gassed with a Thunderbeast Dominus and requires 3 tungsten buffer weights in a SCS but it's extremely positive in cycling and ejection.