Colt “Buntline Special”
A long barreled revolver based on the venerable Single Action Army. It has an extreme barrel length of 16”, although 10” models were available. The name is based off of a Western writer who claimed to have given these long barreled revolvers to several well known figures such as Wyatt Earp.
Note the detachable metal stock. Since there is a 16” barreled version, if the stock were fixed and non-removable, it would be a carbine/rifle. Since it is removable and not a curio and relic/antique, it would be classified as an SBR (Short Barreled Rifle). The BATFE does have certain exemptions for pistols with removable stocks but I don’t think the Buntline is one of the lucky few.