Get one of these. Rand Elite Recoil Shield. They are worth their weight in gold and really work.
I use mine for not only my BPCRs but my other heavy hitters also, (458 Win, 375 H&H, 416 Rigby) plus I use them under my shooting jacket when shooting my steel but plate Vintage Military rifles.
Shooting is suppose to be fun, this recoil shield puts the fun back into the heavy hitters.
PLUS they are legal for use in the CMP's vintage rifle games, where the add on recoil pads aren't.
They are comfortable, and you don't notice you're wearing them until you find the lack of bruises some of those pictures show.