HEY, I resemble that remark!

While I have never loaded a LSWCHP I have loaded some pretty stout 38spl loads. Loads that I will not shoot in an alloy framed revolver, period.

That being said, mixing powders is a risky business even for ammo manufacturers. I would rather think it is some kind of surplus powder, like WC820 or WC297 or any number of those in the AA#9 - H110 range.

Personally, with a steel framed revolver in good shape and in 38spl, I'm not sure you can get enough of a powder of that burn rate in a case that will cause a gun to blow up. Recoil and hit you between the eyes? Sure. Blow up? No. Now, if you were to put a fast burning powder, like say Bullseye or one like that, all bets are off!

I'm thinking that they use SR4756. The reason is ..... because I do! That's as good of logic as most have used here today!

Have fun, be safe.