IS IMR 4320 Too Slow for an M1A?

[clay_breaker]

Read couple articles lately regarding burn rate and M14's. One said use nothing slower than 4064 EVER, the other said use nothing slower than 4320. Well, I had some Hornady 130 SP's laying around and some 4320, neither of which has been used in a long time so I figured I would try it. Found some load data for it stating 45 t0 a max load of 52C. So I loaded up 50 at 47.0 and figured I would just plink with them, didn't expect them to be real accurate. I shot 10 of them over a chrony and got an Av vel of 2955 and they seemed hot. Primers slightly flattened. I didnt shoot any more of them, and am now thinking that 4320 is not well suited to the M14. Your thoughts?

 

[former naval person]

Re: IS IMR 4320 Too Slow for an M1A?

Good powder. Wouldn't use it in a M1 Garand, but the M1A/M14 has an altered gas system that will probably tolerate it. Drop down a grain or two.

 

[clay_breaker]

Re: IS IMR 4320 Too Slow for an M1A?

I might just pull the bullets and back it off a little and see what it looks like. Still doesnt look good for use in M1A. i got a couple pounds 4320, guess i will have to use it up in something else.

 

[former naval person]

Re: IS IMR 4320 Too Slow for an M1A?

For the .375 or .358 Whelen it is the best. The BR guys are buying all they can. It seems to be one of the better powders for the .308. Go to 6mmBR and check it out. You probably need to work up the load rather than just throwing 50 together. JMHO

 

[Grump]

Re: IS IMR 4320 Too Slow for an M1A?

Well, when I plugged my data into QL, assigned an OAL of 2.70 (it's a short bullet but that's a guess anyway) and fudged the burn rate up to give the velocity you report, here's what I got:

Pressure (Pmax): 52734
Barrel time
(10%Pmax to muzzle: 1.004 ms

and an estimated port pressure of 16,019 PSI

All values are piezo, not CUP.

If you're NOT sizing your cases on the short side, you might consider pulling 5 and putting them into cases bumped back, say, .005 from fired dimension, and re-testing. *IF* and only if (did I say IF?) the primer radius has changed to be not so alarming, they might be okay for chamber pressure.

But don't take my word for it. Consider all sources and think it through.

I used 55.28 grains water capacity for the fired case.

 

[clay_breaker]

Re: IS IMR 4320 Too Slow for an M1A?

Thanks for info guys. I'll just stick with my regular M1A load. Pop ther rest of these in a bolt gun.