Bob,
I have 2 special run Thompson / Center Association (TCA) barrels in .22 LR and .44 Mag. Both are 6 1/2", and I have Leupold bases and rings, as well as an Ultra-Dot on each one. The .22 is especially nice as a plinker and all-around fun gun.
The TCA also had a few 6 1/2" .45 ACP barrels made up in a special offer, but I failed to order one at the time, and have never found one since. I wish I had.
I also have a 6 1/2" SSK stubby barrel in .45-70 (!!!), and 2 other SSK stubbies : a 5 1/4" 7.62X25 (marked 7.63 Tokarev). and a 5" .480 Ruger. These last 2 require shortened fore ends.
They're all a lot of fun, but for practical hunting use, I prefer 10" barrels for straight wall cartridges, and 14" for bottlenecks.