I got shipment of powder just before new years and worked up a couple of loads with my Pro Chrono Digital chronograph. None of these loads exceeded the maximum charge listed by the powder manufacturers, but they should be worked up to none the less. Temp was exactly 20 degrees which possibly had an adverse effect on velocity and maybe extreme spreads. All loads were carefully worked up, but  only max loads are listed here. Guns used were a Ruger SP101 with a 2.25" barrel, Ruger GP100 with a 6" barrel for 357 Magnum and A glock 29 with stock 3.78" barrel and a 6" Lonewolf barrel using a 21lb non captive recoil spring in 10mm. None of these loads showed any indication of excessive pressure. The primers looked great and the revolver cases literally fell out of the cylinder after being fired.

First up was the 10mm with 180 grain Zero fmj flatpoints, 13.5 grains AA9 and CCI 300 standard lpp, col 1.255". This is the first time I've used any Accurate powder in 10mm and I'm impressed. I worked up to a max load of 13.5 grains which is what Accurate lists as a maximum load.

3.78" barrel - high - 1134 fps
                      low - 1110 fps
                      ave - 1121
                       es -  24 fps
I'm very pleased with the extreme spread. This load has good accuracy potential and I'll be testing it for accuracy soon..... indoors.

6" barrel - high - 1314 fps
                 low - 1250 fps
                 ave - 1278 fps
                  es - 64 fps
Extreme spread opened up a little with the 6' barrel, but still a good stout load with velocity right  up there with 800x and Longshot.

357 Magnum 170 grain Sierra fmj, 17.5 grains pp300mp, Winchester ssp primer, col 1.585".
2.25" barrel - high - 1105 fps
                      low -  1059 fps
                      ave - 1080 fps
                        es - 46 fps
This powder has not performed good for me with anything under 170 grains and does much better with heavy bullets loaded near max with slight compression. lighter bullets and reduced loads in any bullet weight gave velocity spreads as high as 120 fps and disappointing velocity. IMR 800x and Power Pistol gave just as much velocity with less recoil and half the powder in the little sp101.
                     
6" barrel - High - 1370 fps
                 low -  1322 fps
                 ave - 1344 fps
                   es - 48 fps
Power Pro 300MP really starts to do it's thing in a long barrel with max recommended loads.  17 grains only averaged 1257 fps with an extreme spread of 97 fps.

Alliant recommends standard primers with pp300mp, but I'm thinking magnum primers would provide more consistent velocity since pp300mp is slower than H110 and IMR 4227, but before I try magnum primers I'm going to test again with a firmer crimp. The cases had a barber shop swirl of carbon which leads me to believe they could benefit from a firmer crimp.

These are my two favorite rounds and make up 90 percent of my handgun shooting these days. The other 10 percent being my recent obsession with the 7.62x25 Tokarev round.

The 10mm loads are about what I would expect.  You could take AA#9 up a bit, but of coarse watching for pressure.  Most handloaders accept 14.9grs as maximum with 180gr jacketed bullets.  AA#9 has produced some of the most accurate loads I've shot out of my G20-SF.

About 300MP.  Magnum primers are not necessary and Alliant does not recommend them.  This powder works very well with standard primers.

Ck this post I did a few years ago..

http://smith-wessonforum.com/reloading/267122-357-mag-158gr-study.html

I tested 158gr bullets, but if I could have ever found some Speer 170gr I would load them with 300MP.  I never did, I don't believe Speer makes those anymore.

Thanks for the link there's a wealth of info in that thread

QuoteI tested 158gr bullets, but if I could have ever found some Speer 170gr I would load them with 300MP.  I never did, I don't believe Speer makes those anymore.

Gold dots are hard to come these days especially the 38 caliber Gold Dots. I emailed Alliant and asked them why they only show load data for 38 caliber Gold Dots when they're impossible too find. They said they're working to expand their load data with more bullets and data in the near future.


With 158 grain bullets PP300mp gave the following results

158 grain Nosler jhp, Winchester ssp primer, col 1.590"

18 grains pp300mp

2.25" barrel       6" barrel
ave - 945 fps     ave - 1192 fps
high - 975 fps    high - 1256 fps
low - 909 fps     low 1128 fps
es - 65 fps         es - 128 fps

18.5 grains pp300mp
2.25" barrel          6" barrel
ave - 1040 fps       ave - 1288 fps
high - 1111 fps      high - 1345 fps
low - 987 fps         low - 1242 fps
es - 124 fps           es - 103 fps

These loads were tested a couple of weeks ago
158 grain Nosler jhp, 16 grains h110, CCi 550 spm primer, col 1.590
2.25" barrel
ave - 1050 fps
high - 1067 fps
low - 1018 fps
es - 49 fps
PP300MP is definitely not the same powder as H110.

158 grain Nosler jhp, 8.7 grains 800x, Winchester ssp primer, col 1.590
2.25" barrel
ave - 1018 fps
high - 1034 fps
low - 994 fps
es - 40 fps
800x does pretty good in the short barrel 357. Accuracy was outstanding with less recoil than the slower powders.

Sounds good.  Things will definitely improve when you start shooting in warmer weather.  Doesn't get down to 20° here very often, but when it does I don't do much outside, let alone shoot 

H-110/296 was the powder for .357 for a long time.  Some would argue 2400 was in there also.  But that has all changed now.

I've been sitting on a pound of 2400 for over a year. I't did really good in your tests.

Blue Dot has been one of the best I've used for the 357Mag, 38spl, 44Mag and Spl and even 10mm as well as many others.

I even load my 180gr Speer Silhouette (this is a long bullet) using 11.0 grains and crimped in the normal cannelure for the 357Mag that yields 1320 fps from my 6" S&W Mod 19, they are too long to cycle through the Marlin carbine.
I sent Intercooler some to try and he got this with his Ruger 4" GP100 @ 1237, 1234. Average = 1235.5 FPS/ 610 LBS.


Caliber – 357 Magnum
Powder-Blue Dot 11.0grs
Case – Mixed
Primer – CCI  500
RCBS 180gr Gas Check Silhouette
COL – 1.660"   Sized .358"
Velocity 1320 feet/per sec

Quote from: wadcutter on January 06 2016 08:35:12 PM MST
I've been sitting on a pound of 2400 for over a year. I't did really good in your tests.

Sit no more... load some up!

I retested the 158 grain loads with PP300MP This time with a firm crimp not a wadcutter crimp and just as I thought velocity jumped way up to 1202 fps Ave from the 2.25" barrel SP101 and  1403 fps Ave from the 6" GP100. Extreme spreads also dropped drastically into the 20's from both revolvers. That's more like it.  The cases slid out of the cylinders with no effort and they were very very clean with little if any smearing of the primers.  Very impressed with the velocity from the snub nose, it's withing 100 fps of my hottest  155 grain G29 loads with the stock 3.77" barrel.  The muzzle blast from the SP101 was something to behold and it was loud. Louder than even the Tokarev loads I was testing. It's pretty much impractical for anything but having fun at the range.