The .58 is indeed fun. I have a .58 fullstock Hawken flintlock I made back in the 1970's using a Green River Rifle Works 1/60" twist barrel. In this gun I use both the .570" PRB and the Lyman 57730 570-grain hoillow-base Minie type bullet sized .575".

Both these projectiles are quite accurate using the same charge you used, 120 grains of FFg. Strangely, both of these very dissimilar bullets hit within 1" of one another at 100 yards. This is very handy because the rifle has fixed sights. The PRB load is quite pleasant, but the 570-grainer kinda kicks a little!




Stock is cherry, hardware is silver...... Barrel = 36".