Reassembling AR upper with barrel...

[SD26]

Making some changes on my AR (LR308). As a result, the barrel has been separated from the upper receiver, and I'll be reassembling it soon.

I'm familiar with the standard process, but is there anything that one does for "extra credit"? Meaning, are there any extra steps in the process that can be done to do a better job to maintain previous good accuracy or improve accuracy?

 

[LongArm]

Re: Reassembling AR upper with barrel...

you can bed the barrel extension. I have never done it. I don't think that it is hard. You can also use red loctite #620 on the barrel extension. Just make sure it DOES NOT GET ON THE RECEIVER THREADS. The loctite is used to bed the area between the barrel extension and the receiver NON-PERMANENTLY.

This process is like bedding a bolt action. It makes sure the barrel extension gets 100% contact on the receiver. You could also true the receiver but that would mean taking it to a machine shop.

 

[leadbullet]

Re: Reassembling AR upper with barrel...

best time to clean your barrel the easy way other than that not much you can do that would a difference worth mentioning or noticing.

 

[Temp9]

Re: Reassembling AR upper with barrel...

Don't forget anti-seize.

 

[groundhogbuster]

Re: Reassembling AR upper with barrel...

I'd lapp the upper receiver. It helped a cpl of mine, so I do it to all my upper builds now. And "knock on wood" I have yet to build an upper that didn't shoot at least MOA

 

[SD26]

Re: Reassembling AR upper with barrel...

How does one lap the upper?

 

[biner626]

Re: Reassembling AR upper with barrel...

http://www.pacifictoolandgauge.com/arperformance.htm#arlaptool
I don't know if anyone makes one for a 308.

 

[SD26]

Re: Reassembling AR upper with barrel...

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Biner626</div><div class="ubbcode-body">
I don't know if anyone makes one for a 308. </div></div>
Yeah, that looks to be the problem.

 

[SD26]

Re: Reassembling AR upper with barrel...

Assembled! Didn't machine anything. Haven't gone out to shoot yet either. Happy with the assembly. I'm using a JP handguard that is new to me. Looks nice, and I like the way it feels in my hands along with the KAC micro front sight with a longer sight radius.

Thanks for the input guys!

 

[Ballista One]

Re: Reassembling AR upper with barrel...

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Super Dave</div><div class="ubbcode-body">How does one lap the upper? </div></div>

When a bullet is transiting the barrel, it has no idea that the barrel and upper receiver are not true.

"Lapping" the upper receiver is a questionable modification. There is no empirical data to even suggest it does anything to improve accuracy. Furthermore, if you haven't verified that the collar on your barrel extension and the barrel extension itself are respectively perpendicular and parallel to bore, your wasting time and money. The most you could hope for out of this mod is to reduce the zeroing process by a click or two...

 

[SD26]

Re: Reassembling AR upper with barrel...

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: m_gale</div><div class="ubbcode-body">The most you could hope for out of this mod is to reduce the zeroing process by a click or two... </div></div>That was kind of my thought too. Maybe some friction could be removed from the bolt locking, I suppose, but, given the lack of tools for a 308 and even the possibility of making it worse than the OEM manufacturing...I left it alone.

I did put a little red loctite on the barrel as was suggested. I did actually do a minor assembly on the whole upper, then I torqued on the flash suppressor. Then I backed off the barrel nut and torqued it so that the only input on the barrel, receiver, and nut was from that assembly rather than doing the flash suppressor last. Don't know if it was the wrong thing to do, but it seemed like extra credit to ensure some consistency in the assembly inputs.