That's pretty good thinking!

However, be careful with low-powered loads and lead bullets though, lest you find one of them be-stuck in your barrel with another round traveling down the same barrel behind it. ;-)

I believe you'd find that any primer-only driven load might not have enough steam to push a real lead projectile of stable cross-sectional dimension for it's caliber out of the barrel.

I think I read somewhere that the wax bullets make about 600 fps and might pretty well knock the wind out of a little game animal if it hit them in the right spot. In my Vaquero, though, the wax bullets shoot a few inches lower than my actual point of aim at about 17 feet. They'll hit in about a 1 inch circle with a half-way decent attempt at aiming at that distance.