sound like a grating noise?
if so it might be the spring guide location,for some reason the guide is inside the piston itself so theres nothing in the other end of the spring to prevent it from bending during the cocking process.
i put the guide in the other end of my old .22 hw45 chamber during reassembly after i tuned it up which IIRC prevented the spring bending and reduced the action noise.
beware of stripping your new 45 as the bolt holes are slightly misaligned and the bolts are that tight,they round the hex key holes out.deliberate anti tamper attempt i don't know but damned annoying.
mine is exactly like that and the only way around it is to drill the bolt heads off.