You can't judge chamber length based on whether a gun will accept a particular length loaded shell.
The nominal chamber length is based on the fired hull length. Modern shells are plastic (not paper) and use a folded crimp, rather than an over shot wad and a roll crimp. Modern shells often chamber in a short chamber gun, but it's not safe to shoot them (you‘re probably shooting proof loads). The chamber needs to be long enough to a have the plastic crimp open short of the forcing cone and older guns usually had short forcing cones and tight bore diameters too If the chamber length isn’t marked on the gun (barrel or water table), get a gauge and measure it.
Remember Barry Fain.
Ps. It sounds too expensive for the condition, regardless. I'd keep looking.