I bought two of these and don't have the time or jig to mill them now. These are raw 7075 billet C-4 lowers from New Frontier Armory. Selling both as a package for $75 shipped to CONUS. Cross-posted on another forum.
The blem is that the last round bolt holdback doesn't work with all magazines. I have heard that one could use a AR9 bolt catch with some careful filing to fix this issue. New C-9 bolt catches are available from New Frontier Armory for 9.99 plus shipping for example.
Here is additional info I found on these lowers online. I have not vouched these claims however and these are sold as is.
"This batch of blemished lowers has a functional flaw — The Gap between the bolt catch slot and magazine well is larger than proper mil-spec. A standard AR-15 bolt catch will still function properly when manually engaged however it may not engage the bolt in the locked rearward position when using certain magazines. We find it to hold most magazines well except for PMAG Gen 2 and 3 magazines or magazines with a worn or out of spec follower. When using a standard bolt catch, the only problem you will have with this lower is it may not lock the bolt back automatically on an empty magazine. No other blemishes or issues exist. Another way to remedy this problem would be to purchase a 9mm AR Bolt Catch (C-9 bolt catch) which has a longer trip than a standard catch that can be shortened slightly by grinding or filing and WILL properly hold the bolt open on an empty magazine.
http://i1323.photobucket.com/albums...4-481e-b038-311c78290d4e_zpsd8fjnzko.jpg
