The bullets vary, from copper-jacketed lead to tracer to a "penetrator" round with a tungsten rod centered in a steel core and capped with lead.

I was shooting black powder at a public range in Indiana once and two fellas were on the 100 yard range shooting a) a crew-served WW2 German heavy MG32, tripod mounted, belt fed, machine gun and, b) an AK-47 on full auto doing an "assault walk."

Now I've always felt that crew-served weapons or anything that fires full-auto isn't just for hunting anymore, but I minded my own business. Eventually the idiots other shooters packed it in. About that time a man came up to me with a spent 7.92mm bullet in his hand and asked if this was something I had fired. No, I replied, I'm shooting .50 caliber round ball from a muzzle loader and I'd talk to those guys over there on the 100 yard range.

I don't know if he did or not, but a few minutes later the State Police came around. I was packing up and demonstrated to the cops that I didn't do it -- it's easy to demonstrate your innocence when you're shooting something from the mid-19th Century and the bullet is obviously Not From Then. By then the others had left, but I suppose the police got their names from the range sign-in sheet. I hope they did, anyway.

I've always thought too that if you want to fire machine guns you should join the military. They can better afford the ammunition.