Check the pressure of the reg, it should be around 500psi. If it is showing that then check your o-rings. Only the blue o-ring should be on the hammer. Any other o-ring will cause it to sputter and not recock. Replace the bolt o-rings as I've seen them swell in the past and cause too much friction to operate properly. You can replace the bolt o-rings with c02 o-rings. Check the battery and make sure it is good aswell. Make sure the o-rings are oiled with 100% synthetic paintball oil aswell. #drops on the blue hammer o-ring and 1-2 on the bolt o-rings. No oil will cause alot of troubles, kind of like a car with no oil in it.