Alright alright, tried a few new things
steel bolt lock- lock and release it about 120 times, still in good shape not deformed like the original one. However it just refuse to lock in most of the time semi or auto, may be the spring in the may that pushes the bolt lock is not strong enough to push the heavier steel bolt lock. A solution is yet to be discovered.
New method to reduce fps- all you need is a 7mm bearing from an AEG gear box, plastic one preferably.(thank ASGK for providing this method)
The theory is simple the bearing act as a spacer and pushes the valve forward, hence less gas in allowed into the chamber. I tried to shoot a few rounds and the power is dramatically reduced even though mine M4 is the AFC local version that shoots 400fps+. I don't know if there is any long term problem cause by doing this mod, so DO IT AT YOUR OWN RISK!
