John: Glad you asked. A "BBQ Gun" is also called a "Court Gun" or a "Church Gun". Today the term seems to refer to any overly fancy gun/holster rig that would not typically be worn on duty or in the field.
Historically, the Texas version probably came from south of the border with the Mexican vaqueros who worked on the south Texas ranches in the late 1800's. Mexican cowboys often had fancy, embroidered and/or engraved rigs for their rodeos and other celebrations. A researcher/historian that I respect speculates that the custom was picked up by early Texas Rangers who often had fancy rigs for court appearances or public events (BBQs, etc). Some reportedly believed a fancy rig increased the credibility of their testimony against bad guys. Examples of these may be seen at the Texas Ranger museum in Waco.
By the 1920's it seemed that many southwest lawmen had duty rigs and social rigs. A major law enforcement distributor in Ft. Worth seemed to revel in turning out nickel guns with non wood grips. Wolf & Klar convinced S&W to build the 3rd model 44 with the shrouded ejector for their customers. The company sometimes engraved the guns at their store.
I'm not sure why the term "BBQ guns" became the generic term for these fancy rigs. Hope I haven't bored you to death.
