Upper receiver lapping?

[A5BLASTER]

Here are a couple shots of one I did last Friday. It wasn't as far off as the last one I did, but you can tell in the first shot that it is slightly uneven. The second shot is closer, but still not completely even. I didn't get a shot of the finished upper before the barrel was installed.

I definitely think it's worth taking the time to do. I grease up the lapping tool shaft and use a drill while holding the upper in my hand to reduce lateral loading.

I lock mine vertical in my vice and use my cordless drill to power it as well. Been useing clp on the guide shaft as a lub.

Seems to work good. I typically wait till I have broken the action in by hand cycling a wet bcg/buffer before I go lapp it and install the barrel.

[therealtrikky]

Figured I would document a little bit since this thread has had a little bit of attention & stirred some curiosity. Still waiting on my rail/barrel nut for the AA barrel but figured I'd go ahead & disassemble my PSA upper & check my RRA to see how they measured up. I was somewhat surprised.

First 3 pics are the progression of the PSA upper (12" complete upper buy). It was DEFINITELY off by enough to lead me to think the overall accuracy should be improved (haven't shot to verify). It was a good ways from being true & took a bit more time to lap than I had anticipated. Was also surprised to see no signs of any lubrication or thread locker/anti-seize on the barrel nut.
[ATTACH=CONFIG]15159[/ATTACH][ATTACH=CONFIG]15160[/ATTACH][ATTACH=CONFIG]15161[/ATTACH]

Once I finished with it I started on my rock river upper; this is where I was surprised. It was MUCH further "off" than the PSA and took quite a bit of time to get it lapped enough to get a uniform surface. I'd say I spent probably twice as much time working on the RRA than I did my psa which I was NOT expecting (or maybe my expectations where just in the wrong place?).
[ATTACH=CONFIG]15162[/ATTACH][ATTACH=CONFIG]15163[/ATTACH][ATTACH=CONFIG]15164[/ATTACH]

I will say this has "convinced me" that it's worth doing this from now on. Only one I won't bother with is my AD Reaper 33, but it's been an absolute tack driver since day 1 & far more accurate than I'll ever be (but that's what a "high end" built rifle will do I suppose).