If there was a religion based on the AR-15 modern sporting home defense assault rifle—wait. There is. Tens of thousands of black gun devotees congregate regularly on Internet sites to hash out arguments so arcane they make the first Council of Nicaea seem like Beach Blanket Bingo. One of the greatest debated amongst the don’t-call-them-assault-rifles faithful: gas impingement vs. gas piston. If you know what that means, if you have a firmly held opinion on the subject, you need to read the latest epistle by Hootiehoo at m4carbine.net. And yes, there will be a test afterwards. If not, the SCAR wins. That is all.