I used 2 CVA Barrels in recent builds of Leman Style guns. The top gun is a 45cal barrel from a CVA Kentucky kit and the bottom gun has a 50cal barrel from a CVA Hawken kit. Both of these drums were fitted with 6-1 MM Hot Shot nipples that screwed right in. I wonder if the Squirrel barrel is a different threaded drum? As said above they may have sent mislabeled nipples. Track just sent me two vent liners that were mislabeled a few weeks ago.