ar wrench is correct in the basics, but slightly off in the details....
Commercial loaded ammo uses modern powders with a faster burn rate.
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That should state "SLOWER burn rate".... which is heading toward the "no-no" side for being OK in the M1's gas system.
Way back when the M1 was first being made available to civilian competitive Highpower shooters the Army gave the "gas system safe" ammo rules for the M1 to the NRA and the CMP. They are as follows:
1) NEVER load with bullets HEAVIER than 180 grains
2) NEVER load with powder SLOWER than IMR-4320
These rules STILL apply today.....
Fast burning powders peak in pressure early then drop quickly as the bullet leaves the chamber area. Slower burning powders peak a bit later and at a lower pressure, but the residual pressure remains high all the way out to the end of the barrel..... where the gas port on the M1 is located, hence the need to avoid slower burning powders. Many commercial hunting loads are loaded with powders too slow for the M1's gas system. If you MUST shoot commercial ammo in your M1, equip it with a gas bleed ported lock screw to take the over pressure off the gas system.
Best regards,
Swampy
Garands forever