I can't speak with first-hand knowledge of the Shaw barrel, or the Colt M4 Carbine, but my Wilson .300 Ham'r barrel has an intermediate-length gas tube. It's not one of the regular carbine, mid, or rifle length gas tubes.

Shaw's website says they use a mid-length gas system for their .300 Ham'r barrels. If your Colt uses a carbine-length gas system, you'll need to swap it out for the Shaw barrel.

Thoroughly enjoying Alaska since 2001.