300 MP in 357 Magnum?

[kcofohio]

I have been using 2400 in heavy to full 357 Magnum loads. Seems that 2400 is scarce lately.

But I have seen several listings for Alliant's 300 MP powder. There looks to be some data, not much, but very little feed back on the powder.

I would be using it for paper targets in revolvers, and hopefully soon, a rifle. All in 357 flavor. 140 & 158 gr. lead and jacketed.

Anybody have likes, dislikes for this powder. What should one expect (dirty, filling the case, compressed loads) out of this powder? Alliant's data shows 300 MP exceeding 2400 in weight and velocity.

TIA
kc

 

[RealGun]

The boolit gods haven't blessed it yet, so don't use it on lead. The powder is also plagued by misinformation. I would stay strictly with what Alliant offers in load data and use the same jacketed bullets, no lead or coated lead It is too dangerous to guess or to dignify a SWAG by calling it extrapolation.

 

[Elkins45]

^^^^ I really don't understand how a powder could be suitable for jacketed but not lead bullets. If it's safe under a jacketed bullet it will have even less pressure under lead of the same weight.

 

[joneb]

I've used 300 MP for 44 mag and 22 Hornet with jacketed bullets with very good results, good accuracy low ES #'s and it down loads better than H-110/W296.
I will do some loads with 300 MP for 357 mag. soon as my supply of 2400 is low. Oh wait, I have a # of Accurate #9 so it could be awhile

 

[Reefinmike]

I considered mp300 as my next keg of magnum pistol powder as its a little cheaper than w296 but 300mp requires a heavier charge so that negates the price difference. I stuck with my tried and true w296. It and h110(same thing) are excellent mag pistol powders with superb accuracy and good velocity.

If you really want full magnum loads, try out some lilgun. I dont shoot it often, especially in my revolver, but a max charge pushes a 164gr powder coated lswc 1550fps from a 6" revolver and 2,000 fps from a 16". 200fps faster than w296/h110 max loads. Max lilgun loads really get your blood pumping.

 

[Jlr2267]

It does everything Alliant claims it will. I use it in 44mag and 357. It meters well and does not require a magnum primer (like h110/w296). Max loads in both cartridges are a handful for sure. Only trouble I've had was trying to work up a hot 45LC load for Redhawk (no published loads for this cartridge at the time, maybe still)...for whatever reason, it did not like the increased capacity of the 45LC...the very erratic behavior spooked me and I stopped the experiment. If you want max velocity, this is the powder.

I used it with both hardcast and jacketed xtp...very slight leading with MBC bullets but otherwise it worked very well with both bullet types.

 

[Schwing]

I have used a lot of 300MP powder with fantastic results. The only issue I had initially is that the .357 data in my Hornady manual had start loads that were WAY too low and caused squibs. I have also seen some temperature sensitivity with it at the low end of the data. I had more squibs even with Alliant's minimum load data when it dropped below 10 degrees.

I would never even consider using it with powder puff loads but, if you want to load in the middle to hi end, it is a terrific powder. One of my all time most accurate loads is a Zero brand 158 grain JSP with 17 grains of 300mp. I was seeing 1/2 inch groups at 15 yards (from a rest, I don't shoot that good) and over 1400fps from my 5 inch gp100.

I saw similar results with 240 grain Montana gold JSPs in .44 magnum with 21.5 grains of 300mp. The .44s never gave me squib problems even at lower charges.

There are rumors out there that it is the same powder as h110/w296. This is flat out false. Directly from Alliant, the powder is made in the same factory and is SIMILAR to h110/w296 but is NOT the same and only load data for 300mp should be used.

 

[Elkins45]

There are rumors out there that it is the same powder as h110/w296. This is flat out false.

They don't even look the same.

 

[RealGun]

Testimony sounds like the caution not to use reduced loads applies the same as for H110/W296. I know from my own use that you cannot safely extrapolate reduced loads and loads for lead from the little bit of formal data available. The rule remains to use only proven data, barring extraordinary personal qualifications and resources.

 

[Elkins45]

I know from my own use that you cannot safely extrapolate reduced loads and loads for lead from the little bit of formal data available.

I would agree with half of that. Different powders react wildly differently to reduced loads. They do not, however, have some psychic sense of whether the projectile they are sitting behind has a jacket or not. Pressures are lower with cast lead, but not so much lower that they have the effect of dramatically reducing engraving pressures.

If there's a documented case with any cannister-grade powder where swapping a lead bullet for a jacketed one of the same weight has caused an unsafe condition I am unaware of it. I am willing to change my opinion in response to evidence, but basic physics suggests this isn't a problem.

 

[RealGun]

I hear ya, but I was bullied pretty badly for starting a thread about a 44 Magnum squib with 300-MP and coated lead. You guys are going to be disagreeable regardless.

 

[kcofohio]

Thanks everybody, for their input!

I may only get 1 lb. of 300 MP on my next order. All of the 357 load data I have access to, only Alliant has any listing. And that is only about 3 recipes.

I was avoiding W296/H110, because if I want to have a moderate load, it sounds like I would be on shaky ground.

With IMR 4227, I'm on the impression that if not a full load, the powder can be dirty, or not fully burnt.

I was hoping that 300 MP could fill the gap of 2400's absence.

 

[Elkins45]

I hear ya, but I was bullied pretty badly for starting a thread about a 44 Magnum squib with 300-MP and coated lead. You guys are going to be disagreeable regardless.

I disagree: that's not the same as being disagreeable. I don't think you're a commie or anything.

I bought a pound to see if I could use it in place of 2400 shooing cast lead in 300 blackout. What I discovered is that using the same charge weight that is barely subsonic (1075 fps) under a 200 grain bullet when using 2400 was shooting 675-725 fps using 300-MP. I have a new batch with a higher charge loaded up but haven't had the chance to try them yet. The really interesting part is that even at those extremely slow speeds it still cycled the action on my 10" AR with a pistol-length gas system (suppressed). The gas volume/grain ratio must be pretty high for this stuff.