Cheap safe shells for a test fire

[Bruce P Bruner]

I like these.

[mobirdhunter]

There could potentially be a range of options available at your regular ammo outlets, but you can be sure of RST shells which are loaded to pressures suitable for vintage guns. All this pending examination by an experienced smith.

[Drew Hause]

Having the gun inspected by a double gun specialist is of course the first step. If the smith identifies no cracks in the wood, a tight lock-up, and barrels with adequate wall thickness which are free of defects, any 1 oz. at 1200 fps target load would be a good choice.
Lots of information here
https://www.shotgunworld.com/threads...-shoot.366087/