Unfortunately I can't comment specifically on the MP 540 powder because I have no experience with it. However, based on many of the replies so far, I do have some other comments.
The often prescribed 4895 powder for use in the Garand really only applies to jacketed service type loads. When you switch to using cast bullets, everything changes, and the "normal" rules simply don't apply anymore. This should come as no surprise to anyone who has ever read a handloading manual. If you change one component, you need to reevaluate things.
When we talk about proper powder burn rate for the Garand, you have to keep in mind that we're talking about the pressure at the gas port. When we're talking about a 147-168 grain jacketed bullet at about 2700 fps, then we're looking at powders like 4895, Varget, 4064 and similar ones.
However, when we want to switch to a cast bullet of similar or even heavier weight, we want to drop the velocity to something optimal for cast bullets. So then we drop our (for example) charge of 47 grains of IMR-4895 down to 35 grains. This puts us in the target velocity range of about 1600 - 2000 fps. However, at this point we've also dropped the pressure at the gas port to less than the required ~8k psi, so the action doesn't cycle fully. It may eject the spent brass but not chamber the next round. Or it may not even eject the brass. So then what do we do? We start looking at slower powders to get back to that required port pressure to reliably cycle the action, and yet still remain in that 1600 - 2000 fps velocity range.
Powders like 4350 and 4831 are entirely useful and safe
when used with cast bullets in the Garand at lower cast bullet velocities.
I recognize that some folks will jump all over me and accuse me of heresy with that statement. So be it. I've developed loads with both H4350 and H4831sc and 190-200 grain cast bullets that are not only accurate, but also are very gentle on the op rod.
The sad fact is that a member here, BruceB, who is no longer with us, did quite a bit of development in this area and documented it well, and it's disappointing to me to see that his work seems to be largely forgotten and overlooked now. The thread is here:
https://castboolits.gunloads.com/sho...pringfield-M1A
Bruce started out working on cast loads with his M1A, but then also expanded it to include his Garand. Unfortunately, even though that thread is a sticky in the CB Loads for Military Rifles forum, it seems that very few folks these days have read it. For those wanting to shoot cast in the M1A or Garand, and want their loads to cycle the action, that thread should be required reading.
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Originally Posted by Baltimoreed
