Squaring & Lapping the Upper Face

[Tedward]

I have squared and bedded 3 so far, all CMT Billet uppers, and all Grendels. Unfortunately, none have made it to the range yet. The receivers were probably above average in quality, and still weren't completely square. You can tell by how the finish comes off the end of the receiver. I used the Wheeler lapping tool.

Couple of tips... Oil the bejeesus out of the pilot, and make sure none of the lapping compound makes it into the receiver. That will happen if you pull the tool out too far as you are checking progress.

I can see lapping a forged upper because it is molded/forged.

A billet upper is cut like lapping when it is made to tighter tolerances that you can do with a hand tool. Removing the anodizing is being retroactive to the finish and reducing life of the material. I have a few of the Cross Billet uppers I've been using and have had a machinest check the squareness with his gauges and they were true. He also checked a forged upper and it was not as true so that is another reason why I stopped using the forged uppers. You get a stiffer product (less flex), save time, money and the finish, just go Billet in my opinion.

I did the same for Seekins Mega and a few Mil-spec forged, all billets were true and the forged were pretty good, if you think about it, Forged are also milled when they come out of the line. Look at a raw lower, the main bearing surfaces are put on a CNC or milling machine way better than the hand lapper.....

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