cayugad: My 1999, T/C catalog, # 26, lists the "System One" at 1 in 38" twist rate for the .50, and .54 calibers. Yes there is a 12 guage barrel available, as well as a .32, and .58 caliber. Removable breach plug, and 150 grain capable. You can get a stricker conversion kit, so you can use musket caps, 209 primers, or #11 caps. It is T/C part # 7778. I put this same kit in my T/C Firehawk.