Depending on barrel length, you are going to be in the ball park with a powder charge of .50-60 grains of FFFg powder Check the actual bore diameter, as there a lot of ".45 calibers". If you check Track of the Wolf's Website, and look for .45 caliber ammunition, you will find balls in at least 65 diameters for the various ".45 cal." barrels out there. .430", .440", .445", .451", .454", and .457". I believe that Mowery has a .451" diameter bore, and can shoot either the .440 or .445 accurately.
Check the Rate of Twist( ROT) of the rifling, also. That and the groove depth will tell you if its a round ball, or bullet barrel, that is, whether the ball is designed to shoot Round Balls, or bullets instead. The ROT for RB barrels in that caliber typically run 1:48", but some come with a slower ROT. If the ROT is 1:34" or faster, it was designed to shoot bullets. Bullet barrels tend to have shallow grooves( less than .003" deep), too.
Your .45 cal. Mowery rifle can also be used for casual target shooting, or plinking, with much lighter charges of powder. That 125 grain, plus/minus, ball will kill rabbits and squirrels out to 25 yards with a charge as light as 20 grains of FFFg powder, so don't hesitate to experiement with lighter loads. When you load these guns up to the 65-70 grains range, you are usually looking to do some long range shooting( 100 yds) with your rifle at small targets.
I owned a .45 rifle for years and my target shooting load to 50 yds. was just 50 grains of FFFg behind a .440" ball and a .015" patch. But, as with all guns, I spent weeks trying different powder charges, and ball and patch combinations to find what my particular BARREL liked. Today, I could shorten that process considerably by using my chronograph, but I might not have had nearly as much fun doing all that shooting. :grin: :hmm: :thumbsup: :thumbsup: