Anything is possible. Clarence the cross eyed Brazilian may have been on the model 72 line that day. I would think I would try giving the chamber a really good brushing. It may be possible someone has fired some .22 long rifle in the gun and leaded up the chamber in front of a .22 LR depth and that is keeping a .22 mag from chambering. It is also possible the previous owner may have fired .22 WRF ammo which is slightly shorter than the WMR ammo and still creating a dirty and shorter chamber. Regular .22 LR ammo can be chambered and shot in a .22 WMR and it will screw things up. A .22 WMR cannot be chambered into a .22 LR. Get some good solvent and brush the hades and hopefully the lead out of the chamber. If that doesn't solve the problem, then you need to ship back to Taurus and see if Clarence put your gun together with the wrong barrel. Or tell me what you wat for it and I might buy it.