Christopher
If I was you I would pull those bullets torch the powder and drill holes in the bullets and make fishing sinkers.
I sent some photos to Alan Moon last year of a Tolley ????? which had 4" blown out of the right barrel and a full length split down the left one. This was achieved by its previous owner , A guy in Alaska,using solid bullets, nitro powder and a load supplied by the bullet maker. This rifle now lives in Wisconsin and is awaiting a new set of tubes.
Why not try 120 grns of black and a 365 grn lead bullet to see if it will regulate.
Plaese post some photos of the proof marks asap

good luck and safe shooting
sbs470