Things I learned building this AR

So then, what's your big bore?

Yet...
MUHahahahahaaaa!

Have you thought of a pistol build yet? I'm sure you have a left over detent spring or something without a home.

<*(((>< said:

Have you thought of a pistol build yet? I'm sure you have a left over detent spring or something without a home.

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If he doesn’t have any left over parts, I’m sure I have one or two that I could send him, for temptation.

GunnyUSMC said:

If he doesn’t have any left over parts, I’m sure I have one or two that I could send him, for temptation.

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Planting seeds, I knew you were a farmer deep down in your soul @GunnyUSMC

Ya’ know, @BSA1 , you can always just build another upper to pair with that lower, to limit your preliminary spend on expanding your cartridge catalog...

AR's Anonymous, "where the addiction never stops and neither does the recruiting."

Yeah, I was gonna ask if you lapped the receiver before installing the barrel to make sure the face was square. Doing that would probably have done away with the need for shims as well. I got my lapping tool from Brownell's I believe.

GunnyUSMC said:

If he doesn’t have any left over parts, I’m sure I have one or two that I could send him, for temptation.

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GunnyUSMC- Founder of The High Road GoPartMe.

I like to lap the face of the upper on all of my builds. If there's a high spot, when you torque the barrel nut, you're going to be torquing on the high spot. As you shoot and the barrel heats up, your accuracy may get wonky. You may also find yourself one day wondering why your barrel nut is lose after the high spot wore down.

Wish I had thought to snap some pictures this morning when I assembled one but I’ll try to walk through it with photos I do have or just took.


Tools.


The lapping tool fits inside your stripped upper from the front. The flexible shaft can be chucked into a drill or removed and run by hand.


This is where the lapping compound goes and grinds the face of the threaded portion of the receiver which mates with the barrel extension.


Now cleaned off, you can see where contact was made.


This particular barrel nut must be timed to align the handguard with screws at 3, 6, and 9:00. A standard nut must of course align for the gas tube. Second yellow circle (on the left) shows the area where material was removed prior to barrel insertion and barrel nut being torqued.


Here you can see where the handguard is aligned. The key is to remove just enough material to get everything aligned while staying within torque specs.

I use the same lapping tool as @Skylerbone, I believe it’s a wheeler, but it’s been years ago when in bought it.

If you want to quietly chamber a round on an AR15 a forward assist is absolutely necessary. I frequently find myself using my forward assists on my AR's to fully close the bolt. With out the F/A you need to bump the stock off something solid to get the bolt to close.

Back in 1993 when I went through Army Basic Training, I learned that an M16 that was dragged (low crawled) through mud and sand could be used as a bolt action by using the charging handle and forward assist manually chamber each round.

While the above is good info the requirements of a civilian market don’t necessarily correlate with those of the military and, were it someone’s only AR they could, assuming “troubling times”, carry chambered with safety engaged.

I am OK without the forward assist but prefer a dust cover if possible. My old AR10 doesn't have a forward assist.

BSA1 said:

I tried using the Forward Assist one time and created the mother of all jams.

Never again. If the round doesn’t fully chamber I just recycle the bcg to jack the offending round out and chamber a new one.

My Son who is active U.S. Army as told me the F.A. is useful during qualification due to the poor condition the gun they are given.

When hunting why not carry a round in the chamber with the safety on?

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There may come a time you both need chamber a round quietly and you need every last round you have.

BSA1 said:

shim(s) would still be needed if the barrel nut is bottoming out on the receiver right?

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If the barrel nut is bottoming out then either too much material was removed while lapping or the barrel nut is not in spec or the upper receiver is not in spec or the barrel extension is not in spec or you’re threading it on without a barrel installed. Those are the variables.

Shims can be useful but in my very limited experience I’ve not needed them. Whether there would be circumstances where they are necessary I cannot answer as there are a great number of different barrel nut systems now available that I cannot speak to. Should you run into one of those then I would think the above list still applies and one or more parts is not in spec or has been altered to be out of spec.

Keep this in mind as well; the wear ring on the lapping tool is not from creating a completely flat surface but from wearing down the highest point of the threads. I would estimate that approximately 2/3s of the front face were faced and the remaining 1/3 never touched.