DuMichAuch

The Bolt travel to far back. After that the hammer will bent the edge of the blowback housing to the plastic nozzle. When the bolt travels more back, the hammer will damage the nozzle to and the rifle get jammed... This can happen after modding the backside of the guide rod and shorten the plastic buffer. To soft material at the backside buffer will be compressed to much by blowback.

It will not be a good idea to cock the hammer when the selector is in save position , unlike it is shown in the video. WE only uses a modified M4 Trigger Group. More realistic will be a Trigger mechanism like the upcoming SRC G36. SRC made a copy of the RS-Version and added a valve striker. In save position you can cock the hammer like the RS- G36