Gunsmithing 2. HOW-TO: Ultimate AR Bolt Carrier slickum

[Hellbender]

Part 2:

Now I'll attack the bolt carrier, some of these are so rough (esp. the sliding rail surfaces) they look like a wood rasp.

Use a fine stone and 320 emory paper to smooth up the surfaces shown in the pics below.

Buff them all to a mirror finish when done.

Also slick up the face of the hammer (remove it from the lower receiver) where it slides against the bottom of the Bolt Carrier.

 

[fastford]

Re: 2. HOW-TO: Ultimate AR Bolt Carrier slickum

tag

 

[Powder_Burns]

Re: 2. HOW-TO: Ultimate AR Bolt Carrier slickum

Nice I just found something to do with my free time. Good post.

 

[rankroddin250]

Re: 2. HOW-TO: Ultimate AR Bolt Carrier slickum

or you could just shoot it till all them parts naturally hone them selves. :-D

 

[rero360]

Re: 2. HOW-TO: Ultimate AR Bolt Carrier slickum

I just completed doing these little mods to my bolt and BCG, I didn't do the ejector or the bolt face as I don't have a way to remove the ejector at the moment, and I couldn't find any lapping compound locally so I didn't do that, but it only took me maybe 15 minutes to do everything else.

It does look better and while I can't tell any difference at the moment, the moment of truth will be when and after I hit the range, see if there are any brass shavings inside the bolt afterwards.

 

[OregonShooter]

Re: 2. HOW-TO: Ultimate AR Bolt Carrier slickum

LMT must do this to their stuff already eh? Never seen a "shaving problem" with my LMT upper.

Kinda like "pre-washed" jeans I suppose...

 

[Hellbender]

Re: 2. HOW-TO: Ultimate AR Bolt Carrier slickum

rero360...

The bolt face work in my other thread is the most important thing to reduce shaving problems.

Esp. the small chamfer on the extractor cut (Biggest brass eater) and the ejector pin hole.

OregonShooter....

Brass shaving is not the only (or even the main) reason to do these mods. Consistency in bolt lockup makes for a smoother operation cycle and therefore more consistent accuracy.....

And, NO, LMT (or any manufacturer) does not do these mods to their stuff. A higher quality part MAY have LESS roughness, but it is still a manufactured part.

The brass hardness and smoothness, and pressure of the round will all contribute to brass shaving, also.

 

[rero360]

Re: 2. HOW-TO: Ultimate AR Bolt Carrier slickum

Well I took the extractor out and polished it and the area on the bolt that it sits in just like in your pics, just can't do the whole bolt face and ejector at the moment.

 

[Hellbender]

Re: 2. HOW-TO: Ultimate AR Bolt Carrier slickum

rero360...
That's the most common shaving area, the flat where the extractor sits.

 

[OregonShooter]

Re: 2. HOW-TO: Ultimate AR Bolt Carrier slickum

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Hellbender</div><div class="ubbcode-body">
OregonShooter....

Brass shaving is not the only (or even the main) reason to do these mods. Consistency in bolt lockup makes for a smoother operation cycle and therefore more consistent accuracy.....

And, NO, LMT (or any manufacturer) does not do these mods to their stuff. A higher quality part MAY have LESS roughness, but it is still a manufactured part.

The brass hardness and smoothness, and pressure of the round will all contribute to brass shaving, also.</div></div>

Ah, got it. I guess I can't wrap my head around and AR15 as an accuracy rig and was thinking of it as a carbine, for which I see no purpose of the mods.

 

[PLeighton]

Re: 2. HOW-TO: Ultimate AR Bolt Carrier slickum

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: OregonShooter</div><div class="ubbcode-body">LMT must do this to their stuff already eh? Never seen a "shaving problem" with my LMT upper.

Kinda like "pre-washed" jeans I suppose...</div></div>
The LMT Enhanced BCG has most of this stuff done already.

In this photo you can see the chamfer on the locking lugs and the round bolt face.

For a DI setup, this is money well spent.

 

[Hellbender]

Re: 2. HOW-TO: Ultimate AR Bolt Carrier slickum

OregonShooter.....

Yes, it is hard to change your thinking. BUT, I have a Colt 6920 that when I give it to people (even Pat Rogers at a recent training class I went to) and they pull back the CH, they go "MAN, what did you do to that gun, it feels like it is on ball bearings!!"

Does it really matter? I don't know, but it sure don't hurt, and it will eat anything I can stuff in it!


Dr. Phil....

The LMT has some interesting (and good) features, but can still benefit from some slicking up. and they can't make the lug to bbl extension interface fit as well as a lug lapping job!

 

[PLeighton]

Re: 2. HOW-TO: Ultimate AR Bolt Carrier slickum

Hellbender,

Agreed...
The lug lapping and attention to detail makes a huge difference.
Just wanted to point out how slick the LMT Enhance BCG is.
I've polished mine in most of the same places as you.

By the way, kudos for documenting and sharing this stuff with the community.
Just another fine example of shooters sticking together.

 

[Sean the Nailer]

Re: 2. HOW-TO: Ultimate AR Bolt Carrier slickum

Thank you (re-post before deletion)