Reloading for military semi-autos
Like all ctgs,you are dealing with a pressure bloom of 50,000 PSI a few inches from your face,so prudence is the order of the day.M1/M14 types require extra vigilance at the reloading bench because of the danger of slamfires and out of battery detonation due to improperly prepared handloads.After reloading thousands of rds for these,here are some basic precautions:
1-always FL re-size.Partial or necksizing is OK for a bolt gun because the camming action of the bolt will ensure chambering.This advantage is lacking in the semi-autos which rely on the return spring to chamber the round and close the bolt. Oversize cases which do not chamber easily invite the possibility of out of battery detonation,so make sure that your dies are set up to avoid this.One extra check is to strip the bolt,remove op rod spring and trial chamber each case after re-sizing.Also,make sure case length is within spec.I had one out of battery on a real M14 due to a case which was oversize towards the base,and which did not fully chamber.The case held,and I and rifle were undamaged,but it was a pretty vivid lesson!!!
2-make sure primers are seated slightly below flush with the case head.Use a uniformer on the primer pocket and check this after seating primers.Sit the primed case on a piece of glass and check for rocking or pass a straight edge over the case head.A high primer may be the first thing in contact with the bolt face and you do not want the impact to detonate the primer before chambering occurs.
3-Consider using MILSPEC primers due to the floating firing pin in these rifles which may protrude enough to do more than dimple the primer on feeding/chambering.CCI makes MILSPEC primers,but I have also used WLR and Rem LR without incident.
4-Do not try to economize on brass.4 re-loadings are enough,then discard the brass.The violent bolt action on extracting is very hard on cases.Use the heaviest brass you can find,preferably US GI.
5-Use the correct propellant to generate the proper pressure pulse at the gas port to cycle the action properly.IMR 4895 was MILSPEC for the Garand,but IMR 4064,H4895,IMR 3031 and Varget are fine.Slow burning powders like H4831,IMR 4350,W760 create the wrong gas port pressure and you risk damaging or dismounting the op rod in the process.As a bonus the correct powders are also the most accurate.For 7.62/.308 you can use W748 and BLC2 as well.Garand shooters should also avoid commercial hunting ammo for the same reason as this ammo is generally loaded with slower burning powders to achieve higher velocity.Pressure is OK at the chamber,but wrong for the gas operating system.
6-Only use 147,150,155,165,168 gr bullets in re-loads.Heavier bullets are hard on the rifle-same possible complications as using slow burning powders.
7-Get and use a loading manual.Keeping charges on the milder side is easier on the gun and tend to be more accurate as well.
For additional reference,read the M1/M14 Shop Manual by Jerry Kuhnhausen-it tell you everything you need to know about reloading precautions for these rifles.
]
