MP 638-2 Smokeless Rifle Powder

This is another post about some smokeless rifle powder that I recently purchased on American Reloading’s site and it was described as “Similar to H4831”. They recently published a burn rate chart for their powders going forward. The reference data for it was 2,900fps from 75gr for a 300 Winchester Magnum with a 175gr HPBT. I figured I would give it a try since I also did have some H4831sc on hand to compare it to, and that is a great powder for the 270 Winchester, which is one of my favorites, and the 300 Win Mag, which is also a very reliable favorite for Alaska.

I looked up a starting load of H4831sc on the Hodgdon Reloading site with a 175gr. Sierra HPBT, which I am fairly sure is what the reference data was probably using. That load showed a starting charge of 72gr, at 2,843fps and a max load of 76.5 at 3,006 from a 1:10 twist 24″ barrel. Now, I like Barnes bullets, so I decided to start with the 165 TTSX. The load data from Hodgdon’s and Barnes’s sites showed a starting load for the 165gr at 72gr and 71.9gr respectively, so I settled on a starting load of 72gr and loaded up eight with H4831sc and eight with MP 638-2 to see where they end up with the velocity. I also ran the load through QuickLOAD to get an idea of what I could expect if the MP 638-2 was similar H4831. Looked like 72gr should get me ~2,933 fps from the 24″ barrel of my old Smith & Wesson 1500, which is a Japanese made Howa. It’s a nice rifle, I think S&W only made them for two years. It has the old Redfield wide relief 3-9x scope on it.

My first shot was with the H4831sc load and it clocked 2,962fps. Second shot was 2853fps, so that was quite a spread there, but close enough to the expected load to move on and I was running out of time. Then I tried the MP 638-2. The first one was 2,518, second was 2,539, and third was 2,516. While that was a nice SD, I was not expecting them to be that slow.

When I got home, I ran the numbers through QuickLoad to see what was similar for that charge and speed. First I looked at charges around 75grs that would net around 2,900fps with the 175gr HPBT.

Then I configured QuickLoad to show me the powder list that would be a velocity of 2,524fps with the 165gr TTSX. The powders above are highlighted in blue, and I could see that these were pretty far off. Reloder 25 would have been the closest, but was still nearly seven grains less. I don’t know the fill capacity, but I don’t think it was compressing, or if it was it was very minimal. It looked pretty similar to the H4831sc, which QL was showing at 97%. Based on that, I started looking at some of these powders that are in the green list. Visually, it looks most similar to Retumbo or the ADI AR 2225 powder.

For my next steps, I will work up a ladder test, just going up in 0.5gr increments, and see where that goes, and compare to these powders above in green and see if it looks like a match to any of them. This could end up being a bit slower than what I was hoping for, but we’ll see how it shoots. On the plus side, this could end up being a great powder for the 27 Nosler which needs a bit slower powder than the 300 Win Mag.