I had a gentleman contact me for a .30cal TJ'S barrel for his impact. He had a bit of a twist for this one though. He wants 2 ports. One for pellets and another for slugs. He wants to rotate the barrel 180 deg and change projectiles. Sounds interesting, so I turned it and set it up in the 4axis CNC. Slug port is 100% of bore area and pellet port is 75%. I do believe that It will breath. I'll try and post some pics.