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Power Pro 300-MP, anyone?

Discussion in 'Handloading and Reloading' started by WrongHanded, Jun 15, 2019.

  1. WrongHanded
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    WrongHanded Contributing Member

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    Well, I got 1lb of 300MP from Midway. And after seeing the hazmat fee, added 5,000 CCI 300 primer to the order to try and make it more worthwhile. I'll be ordering from the store in future.

    I started with the Montana Bulletworks 310gr WFN-GC bullet, loading 12 rounds of each charge. 20.0, 21.0, and 21.5grs. Then I took them to the range with my Redhawk. As the charge went up the groups got tighter.

    Back to the house and loaded the last 14 cases with 22.0gr, and back to the range. Another 12 round group was even a little tighter, despite some issues with the gun*. So the groups weren't amazing, but I can tell the potential is there for them to be as accurate as the other load I've worked up with the same bullet.

    I fired the last two through my SBH, to compare the felt recoil to some other loads. These ones are certainly a notch up from my 2400 load. I'll be experimenting more with this powder, but so far I can't find any negatives to complain about.

    *Because I knew I was going to be running some stout loads through the Redhawk, and because I wanted a lighter trigger, I switched the grip and the main spring. The main spring is proving to give 100% reliable ignition so far, even DA. But the Pachmayr Presentation grips are big enough that whilst reducing felt recoil very well, they require a slightly different hold on the gun than I've been used to. And that caused some POA/POI variances during testing.
     
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  2. TfflHndn

    TfflHndn Member

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    I've used it and like it a lot. I always use magnum primers with it, and load it toward the top of its range, just like with W296/H110. It's great out of my Henry Big Boy .357. A GP100 is the only pistol I've run it in so far. Nice fireball! Used 125 grain XTPs and held about a 3 inch group offhand at 25 yards. Was running it side by side with 2400 and it seemed a but livelier than the 2400.
     
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  3. Toprudder

    Toprudder Member

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    Some time ago, I bought a pound of 300-MP to try in 357 mag. I was loading for a 5" Ruger GP100. I made test loads from min to max published values, and about halfway through the charge range the velocity hit a plateau and did not increase at all for an increase in 1.6gn. The velocity that I saw was no better than 2400 (with 158gn bullets) so I set the 300-MP aside and did not use it. I could not understand why the published velocities for it were so much higher than other powders.

    Later, I picked up a 16" 357 carbine and decided to try 300-MP again. This time, I saw a linear increase in velocity all the way up to the max charge, and I was getting ~150fps more velocity than 2400 or H110. So, I believe that 300-MP is good in longer barrels (8" or more) and has no real advantage in shorter barrels. That is when I noticed that the test barrels used for the published data were made with 8" or 10" barrels (Hornady and Alliant, respectively). It has become my favorite powder for my 357 and 44 mag rifles. One nice thing about it, it only requires regular primers, and even at max charges I see no high pressure signs like I see with H-110.
     
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  4. Toprudder

    Toprudder Member

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    Nothing generates as much of a fireball than H110!
     
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  5. kcofohio
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    kcofohio Contributing Member

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    One thing I was disappointed about, was that when Hornady and Lymans came out with their new publication. They didn't cover 300-MP that well in 357. Hornady listed for 125 and 158 gr. Lymans didn't list any. I was hoping to see something for the 180 gr.
     
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  6. kcofohio
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    kcofohio Contributing Member

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  7. kcofohio
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    kcofohio Contributing Member

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    It seems Brian Pierce wrote a few articles about 300-MP in 357. He shows a load for a gas-checked 187 gr. using 17.5 gr. and it is mentioned that data can be used for the 180 gr. XTP. Alliant's data shows a 170 gr. JHP with 18.6 gr. of 300-MP.

    https://grizzlycustom.com/wp-content/uploads/2018/03/Pearce-SBL-Article.pdf
     
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  8. WrongHanded
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    WrongHanded Contributing Member

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    Quick Update: Chronograph

    Using the data from the Brian Pearce article, I loaded some .44 Mag 300gr WFN bullets with 22.0gr, and some .41 Mag 220gr WFN and LFN bullets with 23.0gr. I worked up to these charges, and saw groups tighten as I did so. But I stopped where the article data ended. I should also mention that the .44 Mag 300gr WFN has an actual weight of around 309gr. The .41 Mag 220gr LFN has an actually weight of around 225gr. The .41 Mag 220gr WFN has an actual weight of 230gr. These 'actual' weights are averages from my 5-0-5 scale (for which I have check weights), and included lube and gas checks.

    It was about 66 degrees, and the chrono was 10-12 feet away. Guns used were a .44 mag Redhawk with 5.5" barrel, and a .41 mag Blackhawk with 4.62" barrel. CCI 300 Large Pistol primers were used for all loads.

    .44 Mag 300 WFN / 22.0gr: 12 shots recorded

    Hi - 1235
    Low - 1175
    Average - 1204
    E.S. - 60
    S.D. - 21

    .41 Mag 220gr LFN / 23.0gr: 11 shots

    Hi - 1269
    Low - 1190
    Average - 1234
    E.S. - 79
    S.D. - 25

    .41 Mag 220gr WFN / 23.0gr: 5 shots

    Hi - 1277
    Low - 1202
    Average - 1240
    E.S. - 75
    S.D. - 26


    Now what to compare and contrast that data with? My previous loads using 2400 with both the .44 Mag 300gr WFN, and .41 Mag 220gr WFN, were both "outside of book data". The LBT bullet designs are not included in any manual at my disposal, and the design of these bullets was obviously taking consideration to maximize case capacity.

    However, at only 0.2gr over book data for a .44 Mag 310gr Lee bullet (4th Edit Cast Manual has 16.6gr of 2400 as max) I'd say my load was close to max but likely on the higher side. The same .44 Mag 300gr WFN over 16.8gr of 2400 gave me the following results from the same Redhawk:

    73 degrees, 20 shots.

    Hi - 1149
    Low - 1087
    Average - 1112
    E.S. - 62
    S.D. - 17

    The 300-MP gained me 96fps. Not a huge bump really, but decent. Especially for a 300+gr bullet.

    The .41 Mag data is something I really can't make a solid comparison on, when it comes to "safe" or SAAMI pressure limits. The data I have in my manual says 220gr cast has a Max at 16.2gr of 2400. But older data goes much higher, such as 240gr cast with a Max of 17.5gr of 2400. Now, I will refrain from posting the over book charges I have worked up to using 2400 with the 220gr WFN bullet. But I will say; in my 4.62" BH, these 300-MP loads still beat the chrono data I have for 2400 loads using the same gun and WFN bullet.

    How 300-MP compares to 296/H110, I cannot say. But it's a significant enough step up from 2400 in my guns, that it's worth my continued experimentation. And with standard primers.
     
  9. Thomas Mayberry

    Thomas Mayberry Member

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    Well, as I said in an earlier post I wanted to give 300MP a try in my Marlin .357. I'm glad I did. I was previously using 2400 under a 158 JSP and achieved 1690 FPS with a book maximum charge.

    I obtained a quantity of Remington 158 JSP bullets and loaded up a series of rounds starting at 17.0 grains (Alliant's max is 18.6). I used CCI 500 primers. My rifle is a Marlin 1894CS with a 18.5 inch barrel.

    To keep it brief, velocities increased incrementally with the powder charges and extreme spreads tightened as the charge increased. When I reached 18.3 grains the velocity was 1891 FPS (average for five shots) with an extreme spread of 30 FPS. Since I had reached my predetermined velocity goal I didn't chronograph the 18.6 grain load but did shoot it. There were no signs of excess pressure evident for any of the loads.
     
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  10. buck460XVR

    buck460XVR Member

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    From what I've been told/read, 300-MP was developed by Alliant to compete directly against H110/W296. Being just a tad slower in the burn rate, it was touted as producing a tad faster velocities. Other tout was that it didn't need Magnum primers to ignite. Like others here, I question that assumption. H110/W296 also does not need magnum primers, especially in larger cases like .44 mag and when used with max or close to max charges and a stout crimp. Still it is best to use magnum primers with it, positively with small cases like .357. That is also my opinion with 300-MP. My experience with 300-MP is similar to many here. Very similar velocities and accuracy as H110/W296 with similar projectiles. Like IMR4227, 300-MP seems to prefer long pipes and a heavy projectile.
     
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