Alliant 300MP in the 357 magnum

[JTodd]

Howdy folks,
Im going out to the bench next week to do some load work with the chrono, and my 686. Ill work with several powders, but the real wild card is 300MP. Ive only found two sources for printed load data in 357, the alliant website, and the modern reloading manual, by Richard Lee. The Lee data deoesnt list the primer type, or the barrel length. the alliant site only lists data for 3 gold dot jacketed bullets, using federal 100 primers, which I cant get ahold of. all I have are winchesters and CCIs.

I would like to use 300MP behind the lyman 358156, and 358429, my favorite 357 boolits. Does anyone know where printed data for these might be found, if it exists? Does anyone have any 357 CB experience with 300MP? My normal approach of starting with a reduced powder charge, and working up slowly with the chrono to keep me out of stupid territory wont work here, because I dont know what velocities to expect from my 4 inch, and Ive heard this stuff is intolerant of reduced charges, like H110, but worse. Any advice? Does any one have any experience with the stuff? Thanks!

[MT Chambers]

Handloader magazine did an article on 300mp when it came out, they got the highest velocity of any load using mp 300 in the .357.

[bluejay75]

18 grains behind a 158 grain or 17 behind a 180 grain shoots like magic. Does it at moderate to low pressure so you may not need a gas check. It's the fastest most accurate powder that I load for 357 Magnum. I have never bought standard primers so my loads are shot with either SMPP or SRP.

[JTodd]

Bluejay,

are those 158 and 180 grain cast, or jacketed? thanks!

MT Chambers,
ill try to find that article. thanks for the heads up!

[jaydub in wi]

They also used fed 100 primers in the handloader article. It is issue #274 oct nov 2011.

[bluejay75]

Jacketed and cast in both 158 and 180. I even load 16.5 in 38 special cases with 180 grainers loaded to 357 magnum oal. Accurate but on the sooty side. 17 split too many cases.

With all things start low and work up. In my opinion neither of these are max loads.

[TMenezes]

18 grains behind a 158 grain or 17 behind a 180 grain shoots like magic. Does it at moderate to low pressure so you may not need a gas check. It's the fastest most accurate powder that I load for 357 Magnum. I have never bought standard primers so my loads are shot with either SMPP or SRP.

What he said, if you don't use the Federal's, then use mag primers. Federal's are the hottest non magnum primers which I believe is why Alliant used them, so they could claim their super mag powder doesn't require magnum primers. Also while you can download it a bit, don't go to far. This powder is similar to H110 in that its safer at max load than to under load.

(edit) By the way, the powder charges he quotes are pretty much exactly my recommended loads as well. Plus they are a half grain or so under alliant's max charge so you have plenty of breathing room. Good luck

[JTodd]

Thanks for all of the advice folks! my email notification wasnt working, so i didnt see all of this until just now. good luck!

[curioushooter]

Did any of you try 300MP in 357 out of a rifle? My observations in a 10" contender are shocking...shockingly fast! Another 6-10" inches may ring another 150-500 FPS potentially.

[John Boy]

Alliant 300-MP powder likes magnum primers in any caliber

[curioushooter]

Results for 300 MP out of a 18.5" Remlin 1894c (all loads use Federal 100 primers)
125 Grain XTPHP 21.5 grains of 300 MP (limited due to compression) 2275 average FPS with about a 25 FPS SD. Shoots about 2-3" lower at ~100 yards compared to 158 grain load.
158 Grain XTPFP 18.5 grains of 300 MP (tenth under max) 1875 FPS average FPS with about 20 FPS SD. Very good observed accuracy on gong (loads not bench tested, fired offhand or sitting.

Does Quickload have 300MP yet? If it does it would be great if somebody would run it with 180 grain XTP.

17 sounds reasonable...is this based charge based on anything more than a guess and it hasn't ruined anything yet?

300 MP charge drops 0.9 grains with Alliant's data going up twelve grains 170. That's a quarter grain of charge for ever grain of bullet. That would put a 180 at 16.8. I would use that as a max in a standard revolver. I may be tempted to go beyond that with a heavy revolver or a rifle.

[curioushooter]

I tried federal 200 primers and reduced charges from Hornady's 10th. Perfomace disappointed compared to Alliant's recommendation in revolver and rifle.

[bluejay75]

I have only shot these with Small Rifle Primers. They function in both pistol and rifle well.

[cwlongshot]

Id like to see some data for the 357 maximum or maybe the new 350legend with MP300 myself.

CW

[curioushooter]

Did some more testing in a 1894 Remlin and 20" Henry big boy steel. Single digit variance observed with measure thrown charges of 18.5 grains of 300 mp behind a 158 xtpfp sparked by Fed100: 1902, 1903, 1906 fps. In big boy with heavy octogon barrel (1.5" longer) velocity was 1892, 1892, and 1899. Never have observed such outstanding consistency. Cast boolits are in the menu for some testing this weekend. Oddly the Henry cases expanded noticeably more. Primers looked the same. The Henry's chamber is "looser" it appears.

[Hogokansatsukan]

Did some testing today myself. Very impressed with this powder.
17.0 grains 300mp, Federal SPM Match primer, Starline nickel brass.

NOE 360-182 powder coated and aluminum checked.

Marlin 1894CSBL 16.5 inch S&W 686 5 inch
FPS ft/lbs Std.Dev FPS ft/lbs Std.Dev
FN 180 1805 1302 9 1333 710 27
CN 176 1822 1297 9 1329 690 34
HP 167 1829 1240 17 1326 652 25