brn-180 ?

[Weaver93]

I gotta tell you, if I was shooting more than occasional .25-.33 MOA with a pencil barreled AR with open sights at 100 yds and a flyer opened it up to .75 MOA I would call it a great day at the range.

FYI: I have low expectations for myself and open sights.

My assumption you were at 100 yds.

 

[DSheetz]

Look up Brownells BRN 180 upper receiver detailed overview. They will show the differences in the standard and AR15 style BRN 180 uppers, several changes were incorporated in the AR15 style.

 

[DSheetz]

The piston system used in the BRN 180 is very close to the Adams Arms piston system, the bolt carrier group is different as is the buffering system, but I can see where it might have some bolt tilt but not as easily as the standard AR. With the standard BRN180 the handguard could be a problem with how it is attached to the barrel, which is a slim barrel. All in all, it is a pretty well-designed piece, incorporating things from both the AR and AK.

 

[DDB TX]

Trueing / lapping the upper to the barrel in ARs makes a huge difference in tightening groups. i dont know if the same is true for BRN 180s but it would not surprise me. I built two ARs in 6.5 Grendel using generic uppers and Odin Works barrels that shot about 1/2 inch or less on their 50th through 53rd rounds. Three shots under that dime.

 

[DDB TX]

Trueing / lapping the upper to the barrel in ARs makes a huge difference in tightening groups. i dont know if the same is true for BRN 180s but it would not surprise me. I built two ARs in 6.5 Grendel using generic uppers and Odin Works barrels that shot about 1/2 inch or less on their 50th through 53rd rounds. Three shots under that dime.View attachment 491060

This is the tool I used: Wheeler Delta Series Upper Receiver Lapping Tool for AR-15

 

[Darryle]

Thermal fit uppers are where you see the best start for accuracy provided you begin with a premium barrel.

In the past I used Aero Precision uppers that I would bed the barrel using Loctite 620, but I have since switched to BCM uppers because of the thermal fit eliminating the need for bedding the barrel extension.

 

[TeamCarnage]

I think you need to go back to your load development before blaming the hardware. All rifles are subject to harmonics, if you don't get the powder charge and seating depth optimized, it will have fliers. If you are using the best powder charge of your ladder then adjust seating depth and see if you get a better node.

 

[Catbrain]

definately NOT done tinkering with the load.
FYI-- at 100+ yards---- can get 3 rnds at .3 moa and 2 fliers which are often together bringing the 5 rounds out to 3/4 to 1 moa. My eyes are too old for irons. I am using a PA 5x prism scope. Not much mag-- but exceptionaly clear crisp reticle. Now I am tweaking the powder charge up and down about .2 grains to see if there is any trend. So far all have been mag length.
trying shorter is next.

AR style guns have many good features. Ergo, light weight, modular accessories, ect. I just never liked the DI because it poops where it eats. But it is often frighteningly accurate right out of the box. i have had two in the past that were about 1/2 to 1/4 moa guns.
(if I was careful not to get them hot) One was a 16 in pencil and other was a 16 inch Hbar. Both great pieces.
The pencil was a bushy m-4 like clone without the barrel cut for the launcher. Great gun.

With piston guns having a bag of extra moving parts--
you might expect those could be a source of a slight variability. But in some of them they are pretty linear
in their position and movement. Maybe less chance for lateral slop causing variances. But who really knows on that. No one seems to be researching how to accurize them. (that I can find)

i would like to see a more stable way to attach the handguards. Maybe have it thread on like the barrel goes into the rcvr. with a back up lug and a big nut ?

 

[Catbrain]

I the "thermal fit" way doing a shrink fit ?
(like heat one and chill the other?)

 

[Darryle]

I the "thermal fit" way doing a shrink fit ?
(like heat one and chill the other?)

Exactly, barrel in the freezer, heat lamp on the upper receiver extension.

There are plenty of people accurizing AR rifles, there are also plenty of companies offering precision AR rifles.

The member here @bamban has probably more experience building and accurizing AR rifles than the majority here, IIRC, he builds and maintains the rifles for his clubs shooting team.

Hopefully he'll drop by and offer some insight.

 

[Darryle]

i would like to see a more stable way to attach the handguards. Maybe have it thread on like the barrel goes into the rcvr. with a back up lug and a big nut ?

Like this

 

[Catbrain]

Like this

View attachment 491206

I was thinking of something more aggressive--- like a morse taper with keyways front to back for clock position. This picture looks like it is keyed but looks like
those holes on the side hold it on. Imagine a morse type taper with a compression nut like the AR holds the barrel on. That should be extremely rigid.

 

[Darryle]

The nut is internal, the handguard mount and upper receiver are one piece.

 

[TeamCarnage]

definately NOT done tinkering with the load.
FYI-- at 100+ yards---- can get 3 rnds at .3 moa and 2 fliers which are often together bringing the 5 rounds out to 3/4 to 1 moa. My eyes are too old for irons. I am using a PA 5x prism scope. Not much mag-- but exceptionaly clear crisp reticle. Now I am tweaking the powder charge up and down about .2 grains to see if there is any trend. So far all have been mag length.
trying shorter is next.

AR style guns have many good features. Ergo, light weight, modular accessories, ect. I just never liked the DI because it poops where it eats. But it is often frighteningly accurate right out of the box. i have had two in the past that were about 1/2 to 1/4 moa guns.
(if I was careful not to get them hot) One was a 16 in pencil and other was a 16 inch Hbar. Both great pieces.
The pencil was a bushy m-4 like clone without the barrel cut for the launcher. Great gun.

With piston guns having a bag of extra moving parts--
you might expect those could be a source of a slight variability. But in some of them they are pretty linear
in their position and movement. Maybe less chance for lateral slop causing variances. But who really knows on that. No one seems to be researching how to accurize them. (that I can find)

i would like to see a more stable way to attach the handguards. Maybe have it thread on like the barrel goes into the rcvr. with a back up lug and a big nut ?

From what you are saying I would really focus on seating depth and go shorter in 5 thou increments. If you get one end of the sine curve, fliers will result from the barrel changing direction as it vibrates. You are obviously very close. Eliminating one variable at a time methodically is the answer.