So I was scanning through the new free Alliant reloading manual I got in the mail a few weeks ago and some loads w/Power Pro 300-MP really caught my eye. Sadly they don't list barrel length or pressures.

.357 Magnum data: 125gr Speer GDHP 22.3gr (compressed) @1450fps and 170gr Speer GDSP 17.5gr @1620fps!! I get that it's a little slower powder than 2400, but 1620fps looks like rifle data to me. I would expect a fantastic fireball from the 125gr load, too.

.44 Magnum Data: 200gr Speer Mag HP 29gr @1760fps and Speer 240gr GDSP 25.0gr @1570fps.

So, is this stuff really the magic magnum powder for bullets 158grs and up?

I've got a Henry .44 Mag Big Boy Steel rifle that might be getting some new loads for deer season if it is.

Anyone have first hand experience to confirm this?

I have read of people's testing it and some test were good with heavier crimped cartridges.  It is a damn shame that Alliant is not including any pressure values for their powders in their newer publications. 

I agree Shadow I would really like to know the pressures that are supposedly getting these velocities. I may have to pick up a lb of this and try it out in my 629 and Henry.

Since the 125gr GDHP needs 22.3grs compressed into a .357 mag case to get 1450fps and the 170gr GDSP reaches 1620fps with 17.5grs, my takeaway was that it would take a lot of pressure to get this stuff to burn efficiently. My concern is does it get a little spikey, like 800X?

The 629 and Henry are pretty robust guns, so I'm sure I can work up slowly and be fine. I'd just like to know as much as I can about it before I start.

Lol, absolutely: )

Not to rain on the parade but the article on Power Pro powder at Load Data who tested the Alliant claims found in their testing nothing close to Alliants data. Alliant used a 10" closed chambered barrel like a test barrel which would resemble that of a Contender. Load Data used actual pistols (Rugers) and got something like 500'ps slower than Alliant. Out of a rifle barrel, all bets are off. I would think it would come out mighty strong but until you run it across some screens, it's a best guess. They also recommend magnum primers.

Quote from: Trapper6L on September 03 2018 07:06:26 PM MDT
Not to rain on the parade but the article on Power Pro powder at Load Data who tested the Alliant claims found in their testing nothing close to Alliants data. Alliant used a 10" closed chambered barrel like a test barrel which would resemble that of a Contender. Load Data used actual pistols (Rugers) and got something like 500'ps slower than Alliant. Out of a rifle barrel, all bets are off. I would think it would come out mighty strong but until you run it across some screens, it's a best guess. They also recommend magnum primers.

Thank you Trapper6L! I was obviously suspicious of that data and the 10" closed chambered barrel makes those numbers seem more possible. I may still get a lb to try out against 2400 for rifle loads. A 240gr Gold Dot .44 mag @1570fps out of a revolver would seem to be a VERY stout load. Out of a rifle, not so much.

My accuracy loading for 44 Magnum has been using 16.2 grains of Blue Dot with CCI primers under most 240 grain jacketed bullets.  I even used this same loading with the 255Grain cast Lyman Devastators...  This load is just a little over older book data, but the performance is amazing from my S&W 29 with 8 3/8" barrel out at 100 yards.

I even sent some to Intercooler to test out...
Intercooler test of the  44Mags I sent to him 260 grain Devastators
1436, 1455, 1415, 1456, 1456, 1512, 1457, 1459. Average = 1455.75 FPS/ 1223.20 LBS. Ruger Redhawk 7.5" barrel


260 gr Lyman Devastator HPGC  0.431"
16.2 grains Blue Dot
CCI 350 primer
COAL seated in cannelure 1.692"
Velocity 1370 fps S&W Mod 29 8 3/8" BBL
Energy 1083 ft/lb

38 year old ammo tested
240 gr RCBS Silhouette GC 0.430"
16.2 grains Blue Dot
CCI 350 primer
COAL seated in cannelure 1.654"
Velocity 1360 fps 8 3/8" BBL
Energy 1006 ft/lb

Thanks Shadow. You're both running more barrel than I am. My 629 Classic has a 6 1/2"  barrel w/power port. So I really have to get everything that my powder can give in about 6".

I appreciate the info. May have to give your load a try

I've tested 300mp pretty extensively in 357mag, 454 casull, 480 ruger and 38 casull.  I've tested a few loads in 357 sig and 10mm just to see what could be accomplished and all I get is a massive fireball. In a nutshell 300mp is best as a heavy bullet for caliber powder.  158+ in 357, 300+ in 44 and 45 and it shines with 400s in the 480.

Compared to h110 in straight walled rounds, 300mp grain for grain wont give as much fps as h110 but 300mp runs much lower pressures and is easier to light.  So in total capability 300mp has exceeded my h110 loads but it takes more powder to do it.  Alliant's published velocities are nowhere close to actual velocities and I've seen real world speeds.  I've seen anywhere from 100-300fps less than what's listed in my 6ish" barreled guns.  In the extreme bottlenecked 38 casull (looks like a wsm round) 300mp runs beautifully and obtained very impressive velocities from an autoloader.  The sig does ok with 300mp but it doesn't have as much shoulder on doesn't burn as cleanly as it does in the 38 casull.  In the 10mm velocities were abysmal so it was quickly ditched.

What I have achieved so far:
6.5" 357 blackhawk = 180s over 1600fps (no sticky extraction, max compressed at 1.59", will need to load long for any more)
6.5" 454 bfr = 350s over 1500fps (no sticky extraction but recoil stout)
6.5" 480 Blackhawk = 410gr at 1300fps (no sticky extraction but brutal recoil in the lightweight 49oz revolver)
6" 38 casull glock = 125s at over 1950fps (low case heads and almost mirrors alliant's posted 357 mag data)

Thank you ss30378! Looks like for the 629 Classic the only advantages of using 300mp would be using more of it than H110 and 2400 I still may give it a go in the Henry, just to see what I get out of it.

Your .357 results are pretty impressive! How was the recoil with that one?

In this heavy gun, which is a 6.5" bisley with custom oversized cylinder, 1600fps+ with a 180 is still very soft shooting.  I actually just got the revolver back from reeder with the new cylinder added a few weeks ago.  This 300mp load went 1542fps in the original cylinder (.006 barrel cylinder gap) and 1651fps in the new cylinder (.002 B/C gap).  Over 100fps extra from the new tighter fitted long cylinder!  The most interesting part is this was a 1.59" OAL load.  I can run loads over 1.8" now with this cylinder so once I get some spare time ill work up some long loads and really see what the little 357 can do.   

I run it in 300 Blackout, 357 Mag, 41 Mag and 454 Casull. I've seen noticeable velocity increases when using it vs 110/296. Typically at least 100fps depending on caliber.


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Thanks Mike D, good to know!

This stuff sounds like an improved version of Lil'Gun.  Hopefully we won't be hearing about any horrible side effects from it like the forcing cone issues Lil'Gun has.

Lilgun burns hot, noticeably hot as in i cant touch my barrel after a few rounds hot.  I have not noticed this with 300mp.