The M1 demands the following precautions be observed to ensure safe and smooth functioning:
The ammunition MUST be clean and free of corrosion (a case tumbler or a lot of hand-work polishing each case is a necessity). Clean ammunition will keep the chamber relatively clean and allow the cartridge cases to fully seat, and the bolt to close and lock.
The chamber MUST be kept clean! Dirty chambers can prevent a cartridge case from fully seating and will not allow the bolt to fully close and lock!
The overall length of the cartridge case must be closely monitored, as an overlong case (due to stretching from repeated firings or a new case that is out of specification) can keep the cartridge from fully seating in the chamber. Cartridge cases should be measured before every reloading and kept trimmed to proper length. A cartridge case stuck in the chamber and preventing the bolt from completely closing and locking is asking for trouble. A long or broken firing pin stuck in the forward position coupled with an overlong case, could result in the rifle "firing out of battery" causing a ruptured cartridge case and possibly injuring the shooter with brass fragments or escaping gas.
The primers should be of a lot at least as hard as GI primers. Soft primers can cause slam fires!
The powder used to handload/reload the ammunition used in the M1 must not be too slow burning or too fast... In other words, in order to maintain the proper "gas-port pressure", the cartridge must be loaded to closely match the original loading. A good standard load for the M1 Rifle would utilize a powder with the burning characteristics of IMR 4895, coupled with a bullet of either 172/175 grain weight at approximately 2660 fps., or 150 grain bullet at approximately 2700 fps. Other loads are possible, but must be worked up to with extreme caution.
