I fired my first reloads today. 300-MP in the .44 Magnum, with 200gr XTP bullets. Hornady lists a maximum of 29.9 grains, and a min OAL of 1.60" doing 1600 fps from a 7.5" barrel. Alliant lists a Speer 200gr at a max of 29.0 grains, min OAL of 1.59", and claim it will do 1760 fps from an 8.4" barrel.

I happen to have Hornady bullets (couldn't find Speer) and an 8.4" barrel. So I figured the max load would be somewhere around 1650-1700 fps. The Alliant numbers seem somewhat hard to believe, though the numbers for other stuff like 2400 didn't see dubious, so I wasn't exactly sure what to expect.

I have shot a fair bit of Remington UMC 180 gr JSP, and that stuff is pretty hot. I was sort of thinking that the 300MP numbers might mean similar velocity to the Remington, but with a 20gr heavier bullet. Or that the 300MP numbers were BS... Who knows.

Anyway, I loaded up three loadings to try. I started at 26.9 grains, 10% below the Hornady max. I didn't want to waste a lot of bullets, so I only loaded 5. I would have only done 3, but had some issues getting the crimp I wanted initially. I'm still not totally sure I'm using the Lee FCD to its potential... Anyway, then three with 28.4 grains, and finally I loaded up about 10 at 29.4 grains, the max I tried (.5 grains shy of the listed Hornady max). I loaded them to slightly over 1.60", usually about 1.605", though I do not know how precise my calipers are in that regard. The case mouth was just barely overlapping the crimp groove.

I had a little trouble with the chrono. I shot some PMC over it first to ensure it was reading, but the reloads must have had more blast, because the first two registered as like 500-600 fps until I moved it far enough from me. I also one-handed it at first, in a silly attempt to limit how many hands I'd lose if it all went to hell. So I may not have been shooting perfectly straight across it. Anyway:

26.4 grains: 1516 fps SD: 42
28.4 grains: 1634 fps SD: 26
29.4 grains: 1699 fps SD: 38

That is pretty impressive! That's 1,280 ft-lbs of energy. The Rem UMC 180 grain stuff does 1699 fps from the same gun, though I didn't try it on the same day.

I also shot a few rounds from my 77/44 over the chrono. Just the 29.4 grain loads. It smoked to a 2104 fps average with an SD of 9. That's about 50 fps slower than the 180 gr UMC does from the same rifle. And it is 1,966 ft-lbs of energy.

I do sort of wonder if shooting these full power loads from a S&W 629 will ultimately be a mistake, but they were a lot of fun. I shoot the .44 for fun. I don't have much ability to shoot long distance, I pretty much exclusively shoot offhand. So dialing in accuracy isn't something I'd have much opportunity to do. Blowing up soda cans and milk jugs, and generally getting a good shove, that's what I like about the .44 Mag. So I'm pretty pleased with the powder (though I mainly bought it because it was available). I look forward to loading up some full power .357 rounds as well.

I'm also glad my first reloading endeavor went smoothly, and that the rounds chronographed generally as expected. Though they were a good bit faster than the Hornady manual, and a good bit slower than the Alliant one. I will probably try 29.0 grains and see how that works.

I had no issues with cases being hard to extract. All of the cases, even the starting loads, have very obviously flattened primers. However, I expected as much. All the factory American Eagle and Remington UMC rounds I've shot have resulted in very obviously flattened primers. I forgot to check any rounds that were in the cylinder after firing others, to see if the bullets pulled out of the crimp. I will have to do that next time.