Any oil in the gun can cause the first shot to be high, 12 inches is a lot though. I have seen it up a few inches. If I were you, I would shoot off either a few caps if the gun is an inline or if it is a flint, a little pan powder in the pan or barrel. This way the gun should shoot more accurately.

I would also drop back the charge to 100 grains versus 120. I believe that anything over 100 grains is probably too much. I have shot 150 grain versus 100 in my CVA Firebolt shooting 295 PB or 250 TC Shockwave. I now shoot 100 and it' s enough to hit the target at 100 yards.

Tomster