Question on etchant

Hello, I am rebuilding two antique SxS blackpowder 18 ga shotguns. Both have remnants of a beautiful Damascus pattern underneath the rust, patina etc. What would be the best etchant to use to restore the pattern? I thought about Muriatic acid since it has been used before to etch damascus knife blades but was worried it may be a bit too aggressive and wasn't sure what kind of effect it would have on the solder joints? Any guidance here would be much appreciated.

If your interested in doing-it-yourself you might try to locate this book. It has many formulas. The Modern GunSmith by Howe is another source.