Quote Originally Posted by gnoahhh View Post
So, what effect does high velocity/ high pressure loads with slow burning powder have on the gas operating system of that Garand? Common knowledge has it that slow burning powders give an extended pressure impulse that is very detrimental to the parts of the gas system, which is why the gov't used faster burning powders rather than slow burners for '06 ammo and we civilians are always cautioned to do the same. Are those super high velocity rounds operating within safe pressure parameters to begin with, and do you know that for a fact? Hate to see you come to grief with an heirloom.
To answer all of your questions at once, dad changed the extractor on all of the M1s that he worked on so that if the port pressure become to high it would quickly show some damage to the extractor groove on the head of the case. Start with a light load, and increase it a bit at a time until the extractor marks the groove on the case head and the next charge back from that is the do not exceed. At least they M1 is not as sensitive to port pressure as the Remington 742 and 7400 rifles are. I have seen loads that worked really well in M1 Garands completely wreck those rifles, because the gas port was closer to the chamber.

Best wishes,

Joe