Need 357 data 300MP & Berry's bullets

I just bought some bulk Berry's bullets for 357 mag, 158 grain plated. I'm using starline brass and CCI 500 small pistol primers. I have some Alliant powerpro 300MP powder I'd like to use. Alliant has some data on their site. I believe it is 18.6 grains for 158 hollow points reaching a velocity in the 1600s. I read on berry's bullet site not to exceed 1250 fps. I do not have a chronograph and these will be plinking rounds. I'm looking for some experience and safe loading data. I've never loaded plated or cast bullets before. Thanks.

 

I'm sorry to say but you bought the wrong bullets for full power .357 Magnum loads. As you read they are not constructed for use at those velocities. I would buy a medium burn rate powder like HS-6 or Power Pistol and load them lighter than full power slow powder loads. Better yet, keep those bullets for pressures no higher than .38 Special +P loads. Sorry...

 

Do you have any other powders?

 

300-MP produces some screaming velocities in the .357. At first I thought Alliant was padding their numbers, but when Hornady published similar numbers, I figured it was reality. Even if you can download it sufficiently for plated bullets, I wouldn't. You'll be better off with 2400, Unique or something similar to those two.

 

Thanks for the info. I will buy some different powder and save the 300mp for my hollow points. I did some searching and seems like 2400 is a favorite for 357. I will start looking.

 

If you can't find 2400 there are others that will do almost as well since you can't really push those bullets to top velocities anyway.

Power Pistol, HS-6, Longshot, SR 4756, AA#5 and any other powder in the medium burn rate range will serve you well.

 

I don't have any 158 gr plated, but do have some recent experience with Missouri Bullet Company's 158 grain (Action) SWC bullets. I started at 17.0 grains of 300MP and worked up to 18.3 grains with CCI 500 primers. At 18.0 grains I averaged 1350 fps out of my 4" Ruger GP 100. Brass were easy to extract and primers were not flattened at all. No lead in the barrel. No improvement in velocity was achieved at 18.3, but still no pressure signs either.

I also like 125 grain Berry's plated with 7.0 grains of Unique. Don't have chronograph data on that load, but would guess at around 1000-1100 fps.

 

Part of the problem with loading Berry's in a revolver is that there is no cannelure to crimp into and loading them to legitimate magnum velocities with slow burning powders is asking for bullet jump from recoil, not to mention the inability to get the firm crimp needed for consistent ignition with slow burning powders like 2400. Get yourself some Unique and load them to about 1100 fps.

 

I use Universal for 158gr plated bullets in 357. They break 1100 fps out of my 6.5" Blackhawk and they are accurate loads. Similar burn rate powders should do well too as would a faster powder like 231. Save the 300-MP for jacketed full power loads.

 

A load I have extrapolated for .357 Magnum, 158g LSWC is 14.3 g PowerPro 300-MP. I have yet to test it. As posted on my thread, the VMD for this powder not listed for Lee Auto Disk is the same as AA#9 and W296. That would mean the aperture to try first would be .95.