I called Charles today as it had been two years since I spoke with him about the gun. I remembered incorrectly in my prior post. It's not a bpe but rather prooved originally for 80-570 gr max. Essentially a light nitro, although I don't understand why it isn't stamped cordite. It was reprooved for the 14 ton 577 charge in 1984.

It's heavy enough for the full nitro load but I'm not a fan of reprooving a gun for a heavier charge that it was built for.

I'm sure the gun would have been gone long ago it was originally a full nitro.