I snagged an 80% from ebay. I think it was originally Tannery because it has the uniquely weird ears on the trigger guard.
Mag release went in fine. Mag well finished fine. Trigger guard no problem.
Went to work the top. Everything was going well with large flat file, rat file and sandpaper. Problems came when I tried to figure out how far to go without a jig. I can't find anything anywhere that tells me. I decided to use the bolt catch hole jig I have to let me know. According to it, I went too far.
The exterior top of the buffer tube tower is nowhere near flush with an upper receiver placed in it for comparison.
The tube hole that is in the 80% shows that I still need to take off some from the top rails before centering on the upper. The buffer hole in the 80% looks centered.
The problem is that bolt release. If I put it in with the jig I have, the hole will be very low on the ears. If I center the hole on the ears, the release will sit high on the lower and I'm afraid it will be weak due to the lack of support. Nevermind the fact that it might block the bolt when it shouldn't.
I have compared the 80% to a Stinger lower. Everything looks fine. I can't quite place what is off. It's possible that the 80% tower (properly finished) would never come up flush with the upper like it should. In that case, it is a defective casting, but it doesn't appear to be.
I have since acquired a jig and plan to finish it to see what happens. Might not be a problem.
By the way, I bought it as a CMM if that makes any difference.
Anyone have ideas? Thanks.
Go here: [url]http://quartz2.cyberstation.net/~dwpaul/bs-upper-1.htm[/url]