Will second the comments about a trip to visit George Caswell and tour the gun vault of Champlin's in Enid, Oklahoma. I have kids and grandkids in the OK City area, so while visiting them a couple years ago, I took my son-in-law and grandson and paid a visit to Champlin. As
@ActionBob mentioned, call ahead or email George to set up an appointment. Their building is located at the Enid Airport. It seems that Mr. Champlin was also an aviation enthusiast and owned quite a collection of vintage old aircraft. Champlin's grand dad was one of the original oil tycoons in Oklahoma, so I assume that's where the funding for planes and double guns came from. JJ Perodeau has relocated his shop and I believe it's up around Tulsa.