The hardness of the linotype alloy means they won't bump up in diameter to seal the throats before you can get gas cutting.
I'd try pushing some through the throats on the chambers. If they slip right through then you'd likely be stuck using them for low level loads to avoid leading. But that depends upon whether you have small throats, throats that match your groove diameter or (hopefully) throats that are a little larger than groove diameter.
I'd probably test them out and very quickly ascertain how hard I could push them with whatever powders there were on hand.
Fifty years ago I would have loaded them with Bullseye and put bunnies in the freezer. Grandad loved wabbits.