I had a keel rib fall out of a Simson. Shot it for several years that way with no ill effects. The barrels still retain >95% original blue and I didn't want to reblue them. Had a good 'smith check out the barrels and he soldered the keel back in and cold blued it. You can't tell it's been repaired and I've shot this gun a lot since then. Several thousand rounds and it looks good and the barrels ring like church bells.
Jeff

"We are men of action. Lies do not become us."
Wesley