The main reason to solder is for strength. An old timer told me it was necessary, and I never questioned him. If you have access to a wire edm machine, thats the way to go when cutting doubles and ribbed barrels. Wire edm is an expensive route unless you know somebody, but man do they come out nice, with little to no chance for error, and minimal clean up when your done. Can't beat the old tubing cutter on those plain barrel singles though.