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IMR 4320 and 180gr bullets in the Garand

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Smokey
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IMR 4320 and 180gr bullets in the Garand

#1 Post by Smokey » Sun Dec 24, 2017 8:45 am

Working with Quickload, I entered the data for M2 Ball ammunition. That came to about 2800 fps, 45,500 peak pressure, and a muzzle pressure of 8900 psi. The last is important since that determines operation of the rifle. Too high and there's damage. Too low and it won't cycle properly.

Working with different propellants, IMR4320 gave the best results with 180gr Remington flat-base spitzers (I have a bunch). I could either match the M2 Ball pressures for about 2650 fps, or go to around 2550 fps for a softer cycling load that about duplicates loads for tthe 7.5x55 Swiss. (I've never felt "undergunned" for my furry bad neighbors with that.) I tried the milder loads (8200 psi at the muzzle) they shot extremely well, and cycling was noticebly softer. Case fill was close to 90%, so the ammo will also give less variation from powder position in the case.

This is actually a nice powder to work wih in older battle rifles. It meters well, gives good acccuracy, and has a nice burning curve. It's also sort of an "oddball" that doesn't get much interest with reloaders. That also means it's often not stocked by retailers.
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Re: IMR 4320 and 180gr bullets in the Garand

#2 Post by Polock » Sun Dec 24, 2017 2:17 pm

Smokey--Thanks for the tip. Always looking for good, soft-shooting loads for the M1.
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Re: IMR 4320 and 180gr bullets in the Garand

#3 Post by RWS » Mon Dec 25, 2017 7:06 am

Did you try it at all with 150 grain bullets? Just curious since that's what I have a bunch of.

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Re: IMR 4320 and 180gr bullets in the Garand

#4 Post by Smokey » Mon Dec 25, 2017 5:24 pm

With a 150gr FMJBT loaded to about 2850 fps, I didn't see excessive pressures at the muzzle (or gas port).
You can adjust the pressure curve by playing with seating depth. Deeper seating, higher peak pressure and lower muzzle pressure.
Due to the legal situation, I won't provide actual load data, but IMR4320 seems as if it'll work OK in a Garand.
Of course, you don't want to try to exceed the M2 Ball performance.
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