AR Assembly QC Advice

[rob_s]

I am learning the differences in quality parts vs. crap parts and what makes them different. I understand there are definitive differences.

So, hypothetical situation:
Say I have two rifles, one factory and one assembled at home. I then test both with 1000 rounds of various ammunition types with various magazine under various conditions etc. Both have zero malfunctions not related to ammunition or magazines.

Is there anything specific that would cause the home assembled rifle more likely to have a failure of some component on round 1001 versus the factory gun?

I would start by reading this
Fooled by Randomness By Nassim Nicholas Taleb

[mmc45414]

Non-hypothetically, what part or parts in the above scenario would be most likely to cause a problem? More specifically, excluding quality of parts, what part of the assembly process would be most critical to preventing malfunction? What “QC check” could be done to verify if those critical components were properly interfacing?

I always thought this was useful information:
https://www.slip2000.com/blog/s-w-a-...ine-filthy-14/
And IIRC the bolt was the first thing that failed, and IMO getting a good BCG and a good barrel covers a lot of the potential failure points. Also a lot of the "QC" has to do with metallurgy and is impractical to test or verify, so you need to have a reliable source because you are basically trusting them to have done it right.

Another take-away from the Filthy 14 exercise is that something really has to be screwed up for a direct impingement AR to just not work. They might be over gassed and wear out faster and be less pleasant to shoot, but putting something together that goes bang is pretty well assured. But going bang does not mean it always is going to, forever and ever.

Probably one of the only things you can actually check is the carrier key, and if it gets just a tiny bit loose the thing will quit running.

[Darth_Uno]

I highly recommend getting either the Geissele reaction rod or (significantly) cheaper Brownells version if you intend to build an AR or swap a muzzle device. It makes the process of installing barrels and torquing muzzle devices painless.

Other specialized tools you want to have:
Castle nut wrench
Gas tube roll pin installation punch
Gas tube roll pin removal punch

Generic helpful/necessary tools:
Hammer/mallet
Torch(for removing anything secured with loctite)
Impact driver with impact rated bits
Torque wrench and/or driver
Good 4-6" bench vice

I have the Wheeler reaction rod. Never had any issues installing barrels or muzzle devices. Doesn't mean it's the best but...never had any issues.

The correct roll pin starters and punches will make life 1000000x easier. Cheap investment for heading off frustration and bent pins.

I like the Magpul armorers tool. Kinda pricey and you're possibly just paying for the name, but it is very high quality.

Get a lightweight mallet so you're not beating on your pins with a 20 oz hammer. I actually have a rawhide mallet from my brief foray into leatherworking.

Torque wrench - Most low-profile handguards now have proprietary barrel nuts that don't need to have the gas tube lined up, but you still want to make sure you hit the minimum ft-lb.

Not a tool, but the PWS ratcheting castle nut/QD plate is great. Snugs right up and you don't have to worry about staking it.

[ASH556]

The Geissele Super Reaction Rod holds both the receiver and the barrel extension. I have both the standard and super reaction rods. I use the standard most of the time, but when you're getting paid to work on other people's stuff, it's much more important not to break it and you also can't dictate that your client base only use Colt parts. I user the Super Rod when I'm working on difficult things. Never had a part failure while using it despite having to use cold, heat, and a heckuva lot of force to make some barrel nuts move.

There's also this little gem that I personally take a little pride in:

Mr. Geissele, my Reaction Rod has gotten quite a bit of use since we last talked. Still, I was wondering if there are still plans to bring out the tool we discussed in August with the upper receiver supports in place. I'm assembling a new personal upper (most of my work is customer stuff) with a 12.5" barrel and MK4 Geissele rail. It would be nice to try out the new tool on this assembly if it's close to being ready.

Thanks again for your time and your great contributions to the industry,

Josh Vibert


On Wed, Aug 28, 2013 at 9:43 PM, William Geissele <WHG@geissele.com> wrote:
It was nice talking to you today Josh.

Nate and Stan we will talk about the new tool when we have the first ones. Josh gets the first.

Bill Geissele
Geissele Automatics - We Manufacture Confidence
Sent from my iPad