You could shoot low pressure 2 3/4" shells in a Fox 20 that has 2 1/2" chambers. But if you're going to order RST's anyhow, you might as well get their 2 1/2" shells. Most people that shoot 2 3/4" shells in short chambers are experienced reloaders, and they're reloading to low pressures in their own hulls. SOME factory 2 3/4" shells are loaded to low pressures, and the ammo company (like RST) will tell you what those pressures are. But MOST American factory shells are only loaded to meet SAAMI (American) standards, and they can be higher pressure than what your gun was designed to handle.
