I'm curious as to what kind of velocity can be expected from a 50 cal in-line rifle with a 26-28" barrel using 44 cal 300 grn bullets and 100 grns of Pyrodex or 777?
You'll find velocity and trajectory information for the similar 300 grain .451 bullets contained on the 2 pages of this thread.
Also take note of posts #11 and #13 on page 2.