The three prong suppressor collectors call the tapered three prong was on many of the XM16E1 marked rifles in US Army service and as late as the Mid 1970s some Infantry NCOs would change out the cage for a three prong when they could get away with it then remove it and carry it in their pocket to their next duty station....they were useful for opening crates with steel bands on them. also you could use them as a wire cutter in the same way ( two twisting in opposite directions or one , grab, stretch, and twist) or if in a hurry and in a bad place fork the wire and fire a round.
-kBob