Cabelas has a 72cal double rifle. There are several small custom makers that make 62-72cal rifles that use a pretty stiff charge. James A Gefroh, Ft. Collins Co makes a 62cal halfstock that is a hunting rifle. J P Gunstocks, Las Vegas makes large bore rifles. Pacific Rifle in Oregon used to make some big bore rifles, from 62cal all the way up to 4bore. I'm not sure they are in business anymore. Don't recall seeing an ad by them in over a year. I have read how some people have taken an inline that has a removable barrel and had a large bore round ball shooter made to fit their rifle.