Loading 300 BLK with AA #9 pistol powder

[7SFCW4]

300 BLK loaded with AA #9, thoughts from the lab...

Using data for .357 SIG

Bullet weight, 145 grains, max pressure, 33,000 PSI, velocity = 1170,
charge weight between 9.4 ~ 10.5

Using data for .357 Magnum

Bullet weight, 150 grains, max pressure, 33,540 PSI, velocity = 1394,
charge weight between 12.6 ~ 14.0

Using data for 10MM

Bullet weight, 155 grains, max pressure, 32,700 PSI, velocity = 1414,
charge weight between 14.3 ~ 15.9


Quote from "300 Blackout talk Forum": "...I tried 16.0 grs and 17 grs
of AA#9 with a 150 gr FMJ. I was using formed brass. I blew two
primers out . The primer pockets were expanded so that a primer
would not even seat anymore. So I pulled the rest of them. I know it
will run with 125 gr bullets as the data was published in the most
recent Guns and Ammo issue. My fault I suppose..."

So, it looks like, to me, that we start with a chronograph, a target
and loads beginning with 14.0 grains of AA#9 and work our way up?
Somewhere between 14.0 ~ 15.8 grains should be the desired end state,
the barrel length (16.5 inches and beefier chamber OD vice a pistol
barrel OD should contain the pressure.

Accurate published max pressure for AA#1680, in an AR (16 inch M4
barrel) at 54,564 PSI for a 150 grain projectile.

I can't seem to find any comparison data on burn rate.

What do you think?

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[nwbobber]

There are burn rate charts on the net. Let me google that for you

I don't know what the comparison of a different case, different bore size, has to do with 300 BLK. I don't think you can predict what will happen that way. Be careful.

 

[HandLoad]

I think I would more likely use Date from .357 Mag, as the .300 BLK case capacity is within a couple Cat's Whiskers of that.

You are Really Reaching Far Afield to use .357 SIG data, IMHO.

It is Really Important that You Don't Become a "Test Pilot" when messing with such High Pressures so near Your Eyes and Face, and Your Hands...

 

[nwbobber]

I would be concerned about the different bore size, even though case capacities are similar, all those expanding gases have to escape through a smaller hole, and the projectile moving up the tube makes a smaller difference.

 

[nwbobber]

Looking at accurates 300BLK data http://www.accuratepowder.com/wp-content/uploads/2010/09/300_ACC_Blackout_Data.pdf
It appears that Ramshot enforcer and 4100 must be nearly the same powder, and are very similar in burn rate to #9. It looks like 16.7 max with the FMJ with those powders, I wonder how the grain structure of the powders compare - and why accurate did not test with #9. The guy that blew his primer pockets was in this range with his loads.