You may find that, depending on how the rechambering was done, it may shoot both .45 Colt AND .455. Whilst thinner, the .455 rim is larger in diameter. So if the chambering was done carefully, the .45 Colt reamer made small recesses on the rear face of the chamber, but left enough undisturbed to support the shorter round's rim. I've seen several done that way, and own and shoot one as well. Doesn't seem to hurt accuracy, BTW.