I agree with what has been said above. The RBL 20b is no match for a .577BPE. My Henry shoots a 560grain lead bullet at about 1700 fps. That's a lot of whallop and penetration.

The RBL has a really fast twist. I have seen the twist quoted, but I don't recall now. I think it's less than 20" and designed for a sabot slug. You end up with a light, sub-caliber projectile. Not a big 58 caliber hunk of lead.

Just totally different.

Monty Whitley has a .577BPE at a fairly reasonable price. It's seen some hard use, but may be a good rifle.

http://www.montywhitley.com/antique_arms_fine_sporting_guns/double_rifles/1666

Under $10k is getting low for a .577.

bonanza just bought a nice .577BPE and is getting to know it.

Good luck with your search.

Curl