My brother in law noticed a substantial difference between the accuracy of the black powder loads vs 777. He sighted in his Thompson Center last week with the last of our black powder and had excellent groupings. He switched over to 777 and sighted it yesterday and the gun was shooting very high (1 foot or more at the same distance).

My question is two fold. First, does 777 have that much more energy over black powder that it would cause the gun to be that much off? Second, does black powder lose it's potency over it's life?

Thanks!

Yes, cut your 777 loads back a little and work up again. On the second question, depends if it's been able to absorb moisture from the air. If you keep black dry, it has quite a long shelf life.

Black powder has a shelf life of decades, if not centuries, if it's kept even reasonably dry. If it get damp, it drys well. I haven't heard what the shelf life of 777 is, but Pyrodex looses strength after a few years and the other faux powders like Clean Shot are only good for a year or two.

777 is about 20% stronger than most blacks, with the exception of Swiss. Most muzzleloaders lose accuracy if they're overloaded, but how was the group size with the 777? The gun's still accurate if it's shooting tiny groups even if they're a foot apart with different powders or bullets. You'll just have to sight in for one and stick to it.

Bye
Jack

I actually get a little more careful with 777 in big bores. Does good things in the small bore rifles and percusion revolvers, but pressure does seem higher (hard to judge with accuracy...but 777 shatters percusion caps where loads of fffg doesn't...not much of a indicator, but something has to be shattering those caps).

Don't believe in the tooth fairy...higher velocity is a pretty goodn indicator of higher pressures.

Woudl guess the velocity to be enough higher to produce the differnce in group loaction...probably a bit of barrel harmonics at play here as well.

If you miss the sulphur smell....just stop off at Taco Bell on the way to the range and wait about an hour.

Or, take some pickled eggs along for snacking! :D