I put ~1000 rounds through my Z5-P as a pistol while waiting on my stamp. I noticed that with the stock locking piece, 147gr ammo and octane 45 the bolt was hitting the buffer enough to chew it up a bit. My stamp came in last week and I put on the B&T short stock, USA front grip and a #28 locking piece. I put 500 rounds through it Saturday and I am very happy. Smooth, accurate, no buffer wear at all. It cycles 115 and 147 with and without the stock and octane on it. I shot these at 50 feet with iron sights. Only limitation is my aging eyes. Each target has 30 rounds through it.