What is the maximum powder charge i could use in this rifle?

Like in a .69 springfield M1842 rifle, what is the maximum powder charge that would be safe to use? I think 120 grains of FFg works with roundballs, but if i use 750 grain minie balls would i have to reduce this to avoid an overpreasure explosion? (i think the balls weigh less than half that!) The barrel stell itself is relatively thin, and the minie balls are auctually .04 larger than the bore itself, what would you think would be safe? Thanks!What is the maximum powder charge i could use in this rifle?
a lotWhat is the maximum powder charge i could use in this rifle?
first the below only applies to the rifled musket version of this rifle.


for the smooth bore version use round ball only. as a minie ball will only tumble as it flies down range with the proverbial


';you can't hit the broad side of a barn'; effect.





how do you get a .04 oversize minie ball down the barrel with a hammer.


i would be looking for a .04 undersize bullet mold first.


this will make it easy to reload after the first 4 or 5 rounds.


on the minie ball the skirt expands to seal the bore.


and you should be able to with a clean barrel almost drop the minie ball down the barrel.





next the powder charge. in a large bore like yours i would use Fg powder. it is a slower burning charge. and i would start at about 50 grains and work up 5 grains at a time


you want to fire your rounds into a newspaper filled box.


and dig the rounds out till you can see sharp rifling marks on the minie ball skirt.








this shows that you are getting full skirt expansion and sealing of the bore.





watch that you are getting the right minie balls for your rifle some have a thin skirt and some have a thick skirt for modern inline guns,


you want the thin skirt minies.


then you will find that your shoulder in most cases will tell you the max load.


as most big bore black-powder rifles get unpleasant to fire long before you reach max loads


even then i would not go above 75 gr Fg or 65 FFg with a 750 gr minie ball


also the accuracy will drop off as you get closer to max due to the bullet skirt blowing out (this is why they sell thick skirted minies for the stronger modern in line rifles)
If it is an original rifle, it would be safest to not shoot it at all! The steels used in the original rifles were much milder that those used today in the reproductions. Originals have been known to burst when firing black powder loads.