If you're going to shoot it,
use low pressure loads only. And I don't mean cheap promo loads from wally world.
A laminated-steel, back-action hammergun was almost certainly proofed for black powder only.
There are a couple of companies making low-pressure loads for older guns, that use smokeless powders but stay within the black powder pressure envelope. If you reload, seek out the nitro-for-black loads that have been developed, or load with actual black powder.
Loading with black would seem the safest of all courses, although you must accept the additional cleaning that goes with it. Black powder is pretty forgiving stuff. Modern fast shotshell powders... not so much.
Older guns in good working order can be safe to shoot... if, and only if, you stay within the pressure realms that they were built for. That's not possible with most modern shotshells.
--Shannon