I would caution the OP to do research on up to date references. The chart is wrong. The Stag model 1 I just purchased has M4 feed ramps, an M16 bolt carrier, a black extractor spring insert, and the gas key is staked properly. I didn't go through everything in the chart, these are enough to prove it is not current. It's a good indicator of what to compare though and the spreadsheet has links to a lot of good stuff to know.