Of those who lap your AR uppers (specifically, the mating surface which contacts the barrel extension for headspace), has anyone seen any variability between specific manufacturers and their tolerances/QC in this dimension? I am simply curious and figure this will make for interesting convo… I per…

Hopefully someone can chime in and provide some input for you.

Several Aero & PSA and one unknown brand, no difference to me, they all lapped about the same! I do question if it really makes a difference, I also bed the barrel with blue loctite… i think I’m just wasting my time but since i have the equipment I might as well do it !

I might try a differently marked upper on the next few scratch builds then. I’ve done all palmetto uppers, both built and stripped, and have actually torn them down to lap. I really should do a before and after… it seems on every lapping job with their receivers the high spot is towards the same dir…

Aero, BCM, Rainer Arms, LaRue, Cross Tool & Machine, PSA, Colt…( probably forgotten some brands ) all have benefited from Lapping for me. Large Frame and Small Frame. Have any of them been consistently better then the others… no… not in my experience. They have all varied. Ironically, when I sat…

Huh… that’s good info to know. Thanks, bfoosh!

As bfoosh006 said I always lap my upper revievers. It doesn’t matter who the manufacturer is. It is a cheap and simple process to do so why wouldn’t you do it. When you want the best build possible it is cheap insurance just to do it. Little things really start to add up to overall build quality whe…

Does anyone have any links to a good video explaining “lapping”? I’m new to the AR platform, but currently have 3 builds underway. This is the first time I’ve come across this topic. It hasn’t popped up in any of the research I’ve done thus far. Thanks

https://criterionbarrels.com/media/accurizing-the-ar-15-video-series/?v=00dc5da36527 Part 3 , about the 44 second mark.

I seen lapping before, but never really researched it more as it seemed a bit unnecessary. I am doing my first build soon and wonder if I should bother with it. How would one know if I need to do it and wouldn’t taking off the coating make for a weak point against rusting?

While I understand lapping for precision varmint guns or precision long range, on standard defensive or 3 gun ARs it is equivalent to adding a glass pack to a Civic, the gains are minimal for the time and effort expended. That said, if you have your own tool, do it! Regardless manufacturer you shou…

Upper Receiver Lapping

General Discussion

au2th May 24, 2021, 3:28am 14

I plan on doing this to my uppers. I just need to find the time.

2nd Competition! The Participation Trophy Giveaway! Read the rules please!

Topic		Replies	Views
Aero upper on a PA10 lower AR-10	42	1187	December 28, 2025
AR-10 308 Barrel trued to upper? AR-10	11	900	March 4, 2023
Is Mil-Spec the Luck of the Draw? AR-15	11	456	November 15, 2021
PSA A2 marked lower AR-15	11	768	May 9, 2021
Finally... I bought a PSA AR Upper AR-15	14	6222	April 14, 2023

Upper Receiver Lapping

Related topics