Half way down on a almost close bolt ....safty on,
smack the bold down with a dead blow hammer to size the case, force it into the chamber. Mount rifle in something that holds the rifle, lead sled cleaning fixture, etc, move safely to off, pull trigger with remote string, or wire.
Or unscrew action a quarter turm from barrel barrel, increased head space, the bolt will close, fire remote, as above.
Take the barrel off, tie it down inside a safty area, light a small touch pointed to the primer, get out fast.
Machinist or hobby type thread the barrel, then tap threaded cap for grease fitting fill barrel with oil, cap and pump full of grease until the hydraulic pressure pops out the case.
With the barrel in the lathe, use a sharp trepan tool and coolent...(do not heat up brass case) .. cut brass around the primer, live primer and brass core removed, dump powder, thread tap case head and pull case.