Maximum loads will vary a lot from rifle to rifle and need to be worked up to. I have a .54 Thompsom Renagade that I shot with 110 grains of Pyrodex under a 430 gr maxi ball. It kicked like all get out and accuracy wasn't that good. I dropped it down to 90 grains and with the same bullet sighted in at 100 yards I am good from 50 yards to 150 yards into a 6 inch circle. I could never get that 110 grains of powder to do that. So what I would do if I was you is get the bullet that you want to shoot and work it up from the 90 grains. I think that the recoil will stop you from going too far over the 110 grains. As far a how much powder is really too much, I once heard that you could pack a barrel full of black powder and set it off with out trouble, but then I have never had the urge to try it either.

Who!! Who!! BAD IDEA! The manufacture tells you that 90 gr. of black power is maximum for a reason. The metalurgy of the barrel is probably not up to withstanding the presure of higher loads. You might get away with fireing a few loads but the stress on the metal of the barrel tends to be cumulative, ie: it stresses the metal. As for filling a bbl with black powder, if you put a bullet over it you now have a pipe bomb!.

Is that 90 grns of FF or FFF black powder. because I think that is how ML are rated. 90 grns of FFF is equivalent to about 120 grns of FF BP. Now pyrodex is a difrent story I have never used it so I'm not familier with the conversion, and diferent for 777.
I would go back and read the manual and find out if it is for Black powder or oneof the subsatutes.
My 2 cents
F.K.

Yeah, I shoot black powder 2Fs or Pyrodex RS with Great Plains 425s. Prefer Pyrodex because it's cleaner. The sources I've seen said you can substitute RS for 2F black powder grain for grain, so I shoot 90 gr. with either.

90 grains seems pretty accurate, but I just know I'm giving up a lot of velocity and energy compared to 100 or 110, and that's why I'm asking about those higher loads. I figure I can use all the punch available on elk, assuming it's safe. But now the Old Professor's got me thinking that's not such a good idea. Guess I better just focus on accuracy and shots within 75 yards, in which case 90 grains will be more than enough.

that animal cant tell the difference between 90gr VS 110. Especially when the bullet is so big like the one you are shooting.

Thanks for confirming my thoughts. And you got a cool forum name; maybe we're related???