About four weeks ago one of the local suppliers had some Alliant 300MP powder in stock so I bought a pound to try it out. Alliant lists 18.6 gr as the maximum charge for a 158 gr GDHP which I reduced by 10% to 16.7 gr for a starting load and 17.7 as an intermediate load if the lower load did not indicate any excessive pressure.
I finally got the range on Sunday to test them.
- Gun = Marlin 1894C 18.5" barrel
- Bullet = Magtech 158 gr JSP
- Case = Federal 357 magnum
- Primer = Winchester Small Pistol
- Powder = Alliant 300 MP
- Ambient temperature = 90F (prox)
Results from five measurements (feet/second):
Charge in grains | Average Velocity | Standard Deviation | Maximum Velocity | Minumum Velocity |
16.7 | 1675 | 23 | 1684 | 1635 |
17.7 | 1765 | 24 | 1792 | 1736 |
None of the primers or cases showed any more indication of pressure than normal for a 357 magnum. In fact the Amercan Eagle 158 gr JSP (which clocked at almost exactly 1800 fps) had much flatter primers than the 300MP reloads.
All in all I am pretty impressed with the potential of this powder in a carbine.
No accuracy reports yet. About the time I was getting ready to try some guy started banging away with a neutered version of an M1919 and kicked up so much dust I just packed up and went home.