If there is no round in the chamber my old approach may work:
I took a cylinder head bolt from a Mercedes-Benz S-Class (well, it seemed appropriate in a weird kind of way), placed it in the barrel. Put the gun in a vise and whacked the hell out of it with a hammer, hitting the exposed bolt head.
With a round still in the chamber, this method would not be advisable, unless firing cylinder head bolts through the workshop is your thing