These conversions are pretty cool. I run the newer Black Dog magazines (no screws) and have it installed on a suppressed M16. Zippy little sucker! Fun times. The CMMG conversion is the best I've used. Can't go wrong at $150.
I was thinking about one. Decided to build an AR with a .22lr barrel and BCG instead. Inexpensive to shoot and accurate. Went with the Back Dog mags. No feeding problems.