Anyone lap the upper receiver on their AR builds?

[YBNORMAL]

Although not necessary, I am a bit of a nerd for stuff like that if it helps with accuracy. Wondering if anyone else does it. I was thinking about ordering the lapping tool and truing up the face of all of my ARs, it isn't very expensive.

Internet lore abounds, but I can't see any downside to it, and the upside is better fit from barrel to upper receiver, so larger points of contact between upper and barrel extension "should" lead to a more consistent rifle.

Any experience with it?

[Hodgie]

Out of curiosity I did it on a few after watching this. Admittedly I saw zero difference in any functional way and out of several stripped uppers of different well known brands one being Anderson I only found a negligible amount of high spots on one or two.

It defiantly won’t hurt but I don’t think it’s truly necessary unless your using some real questionable parts which I don’t recommend.

I think proper torque specs are more important then this along with checking for headspace.

[YBNORMAL]

Out of curiosity I did it on a few after watching this. Admittedly I saw zero difference in any functional way and out of several stripped uppers of different well known brands one being Anderson I only found a negligible amount of high spots on one or two.

It defiantly won’t hurt but I don’t think it’s truly necessary unless your using some real questionable parts which I don’t recommend.

I think proper torque specs are more important then this along with checking for headspace.

So......not looking to continue the internet bickering, but.

I put my pistol build together on an Anderson upper/lower, and a cheap (tacfire I think) hand guard, which in my opinion is actually a pretty nice hand guard. I then put a Kaw Valley linear comp on it, the barrel is a 10.5, the comp is 3.25, and the handguard is a 12in, so there is a little less than an inch of the comp sticking out (it looks sick by the way . The KVP comp is super fat and the rail is pretty slim, so there isn't much room for the two to clearance/Clarence each other, and something is crooked, the handguard is touching the comp at about the 2 o'clock position if looking from behind the pistol.

That is the reason I went down this rabbit hole. I have another one of these handguards, a 15in on the other build I just put together, an Anderson upper, RRA 16in heavy barrel. The handguard and barrel appear centered, but admittedly the comp for that build is well out of the handguard so it could be off and would be much harder to see.

My ears are certainly open, but I thought that head space on the AR was the relationship between the barrel extension and the bolt, the barrel doesn't even need to be on the upper to check head space. There are plenty of tutorials for checking head space where the upper isn't even in sight, the proof tool is inserted in a naked barrel, and the bolt is put in the extension and you see if it turns......

So, the only dimension that starts to matter (within reason of course) when taking material off the face of the receiver, is the feed ramps on the barrel extension starting to overhang the corresponding cuts in the lower receiver. Although, if a mag with rounds is inserted, no matter if the left or right round in the mag stack, the tip of the bullet is well above the receiver cuts and is already pointed at the barrel extension cuts (I just checked and hour ago).

I think everyone agrees that doing it has fixed issues with their iron sights being maxed out, I am thinking I may have that problem out of the gate, and if lapping fixes that, it stands to reason it would center the barrel in the hand guard. Yes, I realize that the hand guard could be the problem, but the lapping tool is cheaper than buying a new hand guard on a guess, and like I said, I'm nerd for stuff like that If it doesn't fix it, well, I guess I'll have to look at other hand guards, but I'll have a tool that can quell my ocd on all my rifles. Could be the barrel too, who knows.

[av8tr123]

In my experience (or inexperience)…..

Cheap handguards may yield poor results (off-center, weakness of materials in manufacture, poor design, MADE IN CHINA, etc.).
Some of the less expensive upper receivers may not be as accurately designed (eg.; tolerances not as tight) and manufactured as others that may be more expensive. I have the experience that you get what you pay for.
Some of the less expensive barrels may be manufactured/machined to tolerances that yield poor fitment to the upper receiver.
If you lap the upper receiver too much to affect the feed ramps, you have completely violated the proper function of the AR platform. Lap conservatively.

I use only USA manufactured handguards or "other" handguards with high ratings and reputation. I utilize upper receivers of rated quality (from one USA manufacturer that have extremely tight tolerances and fit) and USA manufactured barrels of documented results/review. Use small parts of better-than-average quality.
I have acquired the tools and devices necessary to assemble/build firearms. When working on the AR platform, I carefully torque/tighten everything to established specification. A hammer is dangerous around an AR. Use a rubber/wood/leather/plastic/acrylic mallet. Apply impact pressure conservatively. Being that the AR has lots of aluminum and steel in close contact, the use of heat and/or cold can be used to ease fit and assembly, when necessary.

[Bang]

I'm wondering how the average bear can blueprint the barrel's mating surface.

[RockIsland]

I'm wondering how the average bear can blueprint the barrel's mating surface.

Machinist's eye.

[Bang]

I guess transfer/disturbance method. Candle smoke the surfaces, carefully assemble and torque, disassemble and check transfer and/or disturbance. Best out of ten tries.

Along those lines...I read that the gas tube contacting anything on the way into the receiver can raise havok with moa quest.

[YBNORMAL]

I'm wondering how the average bear can blueprint the barrel's mating surface.

He can't, but he does what he can.....

The barrel extension is undoubtedly turned on a lathe, so it stands to reason that surface is pretty concentric. The upper, I don't know, I imagine maybe the threads are cut on a lathe, while some type of fixture holds the irregular shape of the upper. Which in my mind is not nearly as precise as using the inside bore of the upper as the reference surface for square, like the lapping tool does.

That's a good question for an upper manufacturer. In fact, here is a video of an upper being machined and the receiver face is cut, and it appears to me that there is no perpendicular reference point for that cut other than the tooling, which can certainly have tolerance issues that stack.

https://www.youtube.com/watch?v=ErrR6x-1RDo

Does anyone doubt the benefit of lapping scope rings? No matter what price point your rings are, it clearly has benefit does it not?

[Bang]

Does anyone doubt the benefit of lapping scope rings

yep. me

Burris has the answer.

[YBNORMAL]

Does anyone doubt the benefit of lapping scope rings

yep. me

Burris has the answer.

So that product was designed to account for manufacturing imperfections.....

Thanks for proving my point that just because a part is precisely machined, doesn't mean it's going to be perfect in it's end use.