I don't know if the semi's are the same as the machine guns. If they are then there are a couple of things that are important. It's been 16 years since my gunners course and I forgot most of it but
1) you have to lock the return spring & rod for the bolt in the bolt assembly before you remove the pistol grip/cover. Be [b]very careful[/b]when removing the grip/cover. That spring is under alot of tension and isn't held in by much. Actually it's held in by a little tab on the guide rod. [b] Don't[/b] have your face down behind the gun when you remove the grip.
2) If you have a failure to fire or it jams..wait 30 seconds before opening the body cover incase you have a hang fire.
Now this info pertains to the model 1919's we had in Canada. This info might not be relavent at all to the semi's.