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I have a question that I'm not sure how to formulate so I'm going to ramble a bit here and try to find a way. I've been using Power Pistol powder for my 10mm reloads and found the perceived recoil with the minimum starting load (8.2 grains with a 180 grain plated bullet) to be similar to many of the commercial 10mm loads on the market. Close enough that I felt I had a good practice round.

I recently picked up some Universal Clays when Power Pistol was all but impossible to find and started working with it. The difference in my starting load (5.4 grains with a 180 grain plated bullet) was startling. The recoil from the Universal starting load felt just like factory 9mm loads. Very little recoil and I could follow up shots really quickly. I know that this all comes down to how the powder burns, but these two powders are almost always listed next to each other on burn rate charts so I figured there were not be a huge difference. So, now for my fumbling questions. Why such a huge difference in perceived recoil from the two minimum starting loads? I thought they would be similar. Will Universal feel more like Power Pistol as I get closer to the maximum load?

Thanks for reading this far! Thoughts? Comments? Criticism?

Somewhere in my fuzzy past I read an article addressing this very same issue. Recoil is a combination of ingredients. You have the weight of the bullet, weight of the powder, velocity of the bullet weight of the gun etc. entering into the equation. Change one or more of these variables and you change the resulting recoil.

Your load with Universal is a relatively light load for the 10mm according to Alliant. I couldn't find 10mm data for Power Pistol with a 180 gr bullet on Alliant's website. Knowing how PP performs I'd say you have a much stiffer load there. If I was trying to replicate the performance of PP I would use Unique or 2400 myself.

Just think of it like sound: even at the same decibel level, certain frequencies sound louder.

Recoil is a lot the same way: even with exactly the same muzzle energy, a lighter/faster load feels different than a heavier/slower load. Generally speaking, fat-and-slow feels more like a push, while light-and-fast is snappier. It's like the difference between a 12 gauge and a .30-06.

Like Mojo said, I think the loads I was using may be off a bit. I consulted a couple of other reloading manuals and they have the Power Pistol starting load a bit lower than what I used and the Universal starting load a bit higher. Should have done a bit more research on this! Lesson learned.

I looked around for some other powders, but Universal was all I could find that would work with several of the calibers I shoot. Luckily, I recently picked up some more PP so I'll move back to it for my next batch.

The rate at which the powder burns could also have an effect. Also I have had pretty good luck with AA 7 with the 10mm

Different powders have different burn rates and characteristics such has how quickly the pressure peaks. This is why some powders are more suitable for one calibre (and/or bullet weight) than another. In general, faster powders will be used for auto pistol cartridges and slower powders will be used for magnum revolver cartridges, though there is some overlap.

for example, blue dot is a slow powder used primarily for magnum rounds (357, 44), but I find it works well in 9mm, but not 460 Rowland.