300 MP in 357 Magnum

Yeah, if you like big fireballs, muzzle blast and recoil then 300 MP is it. The muzzle blast is very intense indoors and if you shoot outdoors the people next to you will move away until you are done firing. Love it.

21 grains behind a 125 grain bullet in a SP101:

Yes Lee Q Loader, that powder is really something, I agree. Like you, I don't care for the blast with the 125gr projectile, but 158gr seem better.
For 125gr I load 2400(R) and Power Pistol(R). The Power Pistol loads are pretty smooth, and 2400 provides plenty of bark for me.
Shoot well,
Paul

H100/W296 is great for fireballs also.

From my testing with 300-MP, I came to the conclusion that it does not offer any advantage in short barrels over other powders, namely 2400 and H110. But I will admit my testing was not extensive, I only tested 158gn bullets, in a 5" GP100, and a 16" Rossi R92.

With the 158gn XTP in the 5" barrel, I did not see any velocity increase in loads from 17.0 - 18.6 gn. That is a full 1.6gn range, with no change in velocity, and essentially the same velocity as I was getting with other magnum powders. I don't remember the recoil/blast being anything unusual. H110 has always seemed to have the loudest bark and flash to me.

When I tried the same load range and bullets in my 16" rifle, though, I saw a steady increase in velocity all the way up to 18.6gn. I also saw the highest velocity of any powder I have tried, and the accuracy was excellent at a charge of 18.1gn. I have also noticed similar results with 300-MP in a 44mag rifle. Those loads also work well in my 10" 44mag revolver, though not as accurate at the max charges. I do like the fact that I can use non-magnum primers with 300-MP and see less pressure signs than with full charges of H110.

I have not tried 300-MP but mostly because I have a good supply of W296/H110 and don't want to buy more powder. From all I've seen W296 produces the same velocities (and fireball) as 300-MP dose.

When you want real magnum ammo you should use a slow pistol powder like W296/H110, 300-MP, Enforcer, 2400 and the like.

I rarely load a bullet lighter than 145gr in the .357 Magnum because I just don't like light bullets.

I tried some loads of 300MP with the 140 gr. XTP bullets in handgun. A little more than my likings at near max. I'll stick with 2400 in handguns.
Now that I have a 77/357, I'm ready to try some serious try-outs with 300MP. Planning on works-ups with 140, 158, and 180 gr. bullets.

Lee Q. Loader said:

Thanks everyone, I guess my purpose with the original question was to see if anyone thought something was wrong. I like shooting the 125 XTP. I think I'll keep loading it along with the 158. It was the most accurate load I've ever shoot with 125's, I'll just get used to the blast. As many have said before, it's nice to not worry about mag primers. I'll be getting more 300 mp!

Click to expand...

If you like your Security Six, you might consider staying with the 158 gr bullets with the slow burning powders and leave the 125 gr bullets with the mid range powders like Unique or Accurate No. 5. Your barrel's forcing cone will thank you. Especially since Ruger is no longer stocking replacement parts for the double action Six series.

I agree, 158gr bullets are kinder to revolvers than lighter bullets. IMO the 158gr bullet can do anything a 125gr bullet can but with more mass.

Sometimes it's nice to be flashy
I use H110 when I get the urge.

Dudedog said:

Sometimes it's nice to be flashy
I use H110 when I get the urge.

Click to expand...

LOL. Same here. I was working up 44mag loads for a Desert Eagle, in both N-110 and H-110. I started with the N-110 first. When I switched to the H-110, I was shocked at how much louder the H-110 was. Then I looked at a slo-mo video my friend took of me, shooting both from the same mag, and noticed the N-110 had hardly any flash, the H-110 was very noticeable. Same velocity, pretty much the same felt recoil. Then I went to an indoor range with the H-110.

Lee Q. Loader said:

I appreciate that advice. My Security Six is an old one. It's the 150 series serial # with the belled grip frame. It was actually my dad's revolver and he always shot 38's in it. I always read about flame cutting being the main problem shooting hot 125's. What is the issue with the forcing cone? I do love my Six and want to pass it to my kids.

Click to expand...

The same hot gas and powder that can flame cut the top strap also is slowly eroding the forcing cone of the barrel. The more powder you use (compounded by lighter weight bullets) the faster it occurs. I am cautious with my vintage Smith & Wesson Model 28 Highway Patrolman, for that reason. Barrels aren't readily available once it wears out. My much newer GP-100, not so much, so I can abuse it at will.

The same hot gas and powder that can flame cut the top strap also is slowly eroding the forcing cone of the barrel. The more powder you use (compounded by lighter weight bullets) the faster it occurs. I am cautious with my vintage Smith & Wesson Model 28 Highway Patrolman, for that reason. Barrels aren't readily available once it wears out. My much newer GP-100, not so much, so I can abuse it at will

Click to expand...

Me too. I don't shoot my 1957 28 much any more. I also use a GP100 when I feel like shooting heavy loads. I don't mind the extra recoil.

Sometimes it's nice to be flashy
I use H110 when I get the urge.

Click to expand...

I use loads like that to move an obnoxious shooter away from me at the indoor range I use. Reading this post I may have to get some mp300 and try it out. It wasn't available to me 3 years ago, when I had my accident and wrecked my knee and had to stop shooting because Obama Care cost me 7 grand to get it fixed. Two years of hobbling around but now I'm walking better and it's' good to be shooting again and have some catching up to do.
I still favor high pressure loads in my hand guns and look forward to this.

With the 158gn XTP in the 5" barrel, I did not see any velocity increase in loads from 17.0 - 18.6 gn. That is a full 1.6gn range, with no change in velocity, and essentially the same velocity as I was getting with other magnum powders.

Click to expand...

I will have to try that with my 4" GP100 and see if I get the same results, but quicker due to a shorter barrel. But I have to wait until Christmas when I get my LabRadar. I can use it in the indoor range I am using now. It will be nice to know what velocities I get with my most accurate loads and will be nice to be able to say what velocities get with them. I've always been jealous of those of you that have Chronographs and your own ranges.

tightgroup tiger said:

I will have to try that with my 4" GP100 and see if I get the same results, but quicker due to a shorter barrel. But I have to wait until Christmas when I get my LabRadar. I can use it in the indoor range I am using now. It will be nice to know what velocities I get with my most accurate loads and will be nice to be able to say what velocities get with them. I've always been jealous of those of you that have Chronographs and your own ranges.

Click to expand...

Would like to know how it works for you, and see if it compares with my results.

As far as moving an obnoxious shooter at the range, that is what I like to use my 460 for. I load that with 200gn bullets and 49.0gn of H-110. BADA BOOM. LOL