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Alliant 300-MP in the .357 Magnum

Discussion in 'Handloading and Reloading' started by nody, May 25, 2012.

  1. nody

    nody Well-Known Member

    I did a search on 300-MP, and no thread came up on this relatively new powder, so I'll start a new one…

    300-MP is a great powder, and at $3+ less per pound than H110/WW296, a bargain. It is as clean or cleaner than 296, and far cleaner than my old favorite, 2400. I could not get 2400 levels of accuracy with 296, but 300-MP is even more accurate than 2400, in my testing.

    Here's what they both look like up close:


    296 up close:


    300-MP up close:

    Some background on 300-MP from an expert of Handloader Magazine:


    Using Hodgdon and Alliant data for jacketed 158 gr bullets, because published data for lead bullets always assumes swaged and hence low velocity loads, I worked up ladders on 296 and 300-MP. Common to all loads:

    S&W 586-0, 6" bbl, factory Partridge iron sights, range 50 feet

    Missouri Bullet Co 158 cast SWC, BHN 18

    Starline once fired .357 Magnum brass.

    Winchester Small Pistol Magnum Primer, though Alliant says a mag primer is unnecessary, the Handloader article says he had better consistency and velocity with mag primers.

    There was NO lead accumulation in barrel, other than the smear of lube that was the same after one or 100 rounds, and came right out with a WD-40 wet brass brush and one pass.

    All case diameters were mic'd before and after firing. Conventional wisdom is that 5 thousandths of an inch (.005) is a "poor man's" sign of a reasonable upper pressure limit, and more accurate than flattened primers. Winchester primers (brass) flatten while CCIs (nickel) don't with the same load, for example.

    The upper 296 loads ran to 6 thousandths (.006), but all 300-MP loads stayed at or below .0045.

    This was the most accurate 296 load:


    All the 300-MP loads were on average more accurate than their 296 counterparts, and this was my best 300-MP load:


    My favorite 2400 load:


    Disclaimer: These loads were carefully researched, measured, and worked up. I do not endorse them for your use, as I have no control over your actions.
  2. 4895

    4895 Well-Known Member

    I feel married to H110 for .357 mag. loads but have been curious about 300-MP as I have seen some great numbers in the Alliant load manual. How is the flash and recoil compared to W296?
  3. 7mmb

    7mmb Well-Known Member

    I'm almost out of the 8lb jug of N110 I bought years ago for 357 Mag. I'm looking for a new powder because N110 is no longer sold except in one pound canisters and is hard to find and much more expensive. I tried most of the magnum powders before settling on N110. I may need to get a pound of 300-MP and try it out. My only problem is the slim amount of data for it compared to the rest.
  4. Crashbox

    Crashbox Well-Known Member

    I bought a pound of it about a year ago but never loaded any up, this may well encourage me to do so...!

    Is the fireball anything like 2400 puts out?
  5. gamestalker

    gamestalker member

    I have to admit I'm as sincerely loyal to 296 / H110, as I am to my wife, and for about as for long too, 3+ decades of loyalty. But I have been reading up on 300MP, and I have the new Alliant load book I've been checking out as well. Since I only run 296 loads through my magnum wheel guns, 296 has fit the bill perfectly in both velocity and accuracy performance.

    I use CCI 550's, and with my 296 loads, the primer pockets are filled to the edges and as flat as a level, yet I still get endless brass life spans it seems.

    What kind of velocities is 300MP delivering with 158's? I won't load with a magnum powder that can't keep up with 296. I'm the kind of handguner that likes power house loads that are all out, so is 300MP all out?

    I'm not really in to economics either, so my sole focus is velocity and accuracy. And yes, both of those elements can live together in the same phrase. I personally feel that a lot of problems some have with accuracy from all out powders is recoil perception, and reaction. I have a model 66 that is a S&W custom job, and from a rested postion, that snub will cut the center out of the target at 50' with 296 reloads with me behind it. Yet someone else who has never shot a 296 magnum load will not commonly get the same kind of accuracy performance, especially after the first hammer drop. 296 can be very intimidating, especially for someone who doesn't usually shoot full house magnums.

  6. nody

    nody Well-Known Member

    I have only fired it outdoors on sunny days, so I cannot really attest to the flash, though I noticed none. A comment by an Alliant rep on another forum says it has NO flash suppressant.

    Recoil I felt was less sharp than 296. I shoot only full house loads and only cast bullets, and I shoot a lot of them, so as you know your either develop "a feel," or at least you think you do. ;)

    Generally, sharpness of recoil follows speed of the powder, with the obvious exception that you can't get full house loads out of say Bullseye. But I do notice my 6.5 gr Unique is sharper than the 13.5 2400, even though the latter hits the steel a lot harder, is louder, and so on.

    As for the report, the 300-MP is a little more bass than the 296. I like it better.

    Powder Valley has about the best prices out there, and 300-MP is $109.50 for a jug, while H110 is $129.50 and WW296 is $131.35. Then again, you CAN use a little more 300-MP, so the price differential may be less than at first blush.

    My most accurate load with 296 is 15.0, while 16.0 with MP was slightly more accurate than that. However, it really tightened up at 18.0 and 18.5. Alliant lists 18.6 as a max, btw.

    I think there may be some pressure spike similarities with the MP as with 296 in reduced loads. I started out below 10% on the ladder and the case mic's were less at 18 than they were at 14.

    You do not see that with 2400; it's more of a straight line variation. Of course a Contender is the best way to check this, assuming one does not have access to a pressure barrel. I do track the individual chambers for variations, and adjust the numbers accordingly.

    As for velocities, I don't have a chono, but the MP shows higher numbers, and should be, being slower and with higher charge weights. I think the goal of 300-MP is to be a 296 killer; it does everything better, cheaper, and with a standard primer, is I guess "the theory."

    As for comparisons to Li'l Gun, I don't think they are appropos; Li'l has a bad rep for eating guns, and is an entirely different animal from what I have read.

    I think Alliant realized that just cleaning up 2400 wasn't enough, and Hodgdon was cornering the market since they bought out the WW line.

    You guys are right about the lack of data out there; Alliant really doesn't seem to be too interested in marketing this powder, other than by price.:confused:
    Last edited: May 25, 2012
  7. ArchAngelCD

    ArchAngelCD Well-Known Member

    Thanks for the extensive report nody...
  8. 4895

    4895 Well-Known Member

    Yes! Thank you for the report. I will have to buy a lb. next trip to try out.
  9. Crashbox

    Crashbox Well-Known Member

    Nody- I also thank you for this report, it has indeed been quite helpful.
  10. gamestalker

    gamestalker member

    I'm really impressed with your report, good job! I'm now very interested in giving it a try. I honesly didn't think you could go slower burning with magnum powders than 296, without sacrificing some magnum performance. I'll have to load some up and chrony them side by side my 296 loads.
    Thanks for the over view.
  11. ArchAngelCD

    ArchAngelCD Well-Known Member

    I would like to see a side-by-side with W296, Lil'Gun and 300MP. I'm guessing Lil'Gun will produce the highest velocities since my tests in a Carbine with Li'Gun and W296 with 170gr and 180gr bullets in the .357 Magnum shows Lil'Gun to be superior by a lot. (100 fps or more)
  12. nody

    nody Well-Known Member

    I'm sure you are correct Arch.

    The stated concern with L'il is the heat generated, forcing come erosion, and flame cutting. Mind you, I have no personal experience with L'il, and I aware that much of the "drama" in the reloading world may be overblown.

    I think a three way velocity test might be very interesting. If I buy a chronograph, I'll run one.

    My main interest in the MP was higher velocity with better accuracy, at lower temperature, and anecdotally it appears to deliver.

    Price-wise, comparing 16 gr of H110 to 18 gr of MP, the latter is about 15% cheaper, but you use about 15% more, so that's a wash.

    These days it seems mag primers cost the same and often have better availability than STD, so 300-MP's use of standard primers is of limited advantage.

    Mostly, it is something new and interesting, and fertile for experimentation, there being not only so little data out there, but nil in the way of educated discussion. I read every thread on every forum I could find, and there was doodly squat to be found.

    300-MP jas some potential for increased performance. I think as one gets into the heavier bullets they may find more advantage with the slower powder.

    A real place where it's reported with experience to shine is bettering the already excellent .410 hull life of H110.

    One thing is certain; Alliant needs to get off their butt. I have been a long term fan of Hercules, but with ATK getting more and more into Big Gov't, that huge homeland security .40 cal buy specifically, my loyalty is waning.

    Then again who am I kidding? H110/WW296 is made by General Dynamics, and so is MP. ;)
    Last edited: May 28, 2012
  13. ArchAngelCD

    ArchAngelCD Well-Known Member

    I don't remember which magazine but there was a review done recently and while they claimed 300MP was a good powder nothing in the article made me think it was superior to the others now on the market. That's too bad because we are always looking for a better powder! (well, at least some of us LOL)
  14. nody

    nody Well-Known Member

    One thing I forgot to mention about the 300-MP loads:

    At 13.0 grains the power depth is .375 from the case mouth, so with a standard 158 SWC the powder is not compressed. At 18.0 grains the depth is .355, and the powder is slighty compressed.

    A small detail that may be of interest.

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