I have not done this in a while but this is what I think i recall. After removing the cap you have to unscrew the mag tube by putting a punch in the screw holes on the end of the tube (counterclockwise of course). Then you drift that tenon out to the right and remove the handguard.
Yes, 71 tubes are threaded and screwed in. Be careful not to damage the screw holes in the tube when unscrewing it
