I am pretty sure Ruger wont sell you the barrel without sending them the gun. They are kind of funny about selling some parts. I have seen some Ruger guns with Smith barrels and some with Colt Python barrels! So, that may be an option, but don't quote me on that. They may have to be re-threaded to work, I don't know. To cut the end that attaches you would have to have a way to re-do the barrel shank and re-thread and re-chamber it, a pretty involved, costly proposition. Honestly, it truly would probably be cheaper in the long run to trade the 6 inch for a 4 inch than to have a gunsmith shorten the barrel. I toyed with the idea of shortening a 7 1/2 Redhawk I used to own to 4 inches (before Ruger came out with the 4 inch) but most places wanted about $150-$200 to do this. I said screw that and just sold the gun. When Ruger came out with the 4 incher I had to have one.