Jay, Idaho
If i can recall, Charles Bailey's tube gun looked a little like the USS Enterprise out of Startrek, where it had two pods that ran in seperate bags, and the tube was something in the vacinity of a six inch diameter bore casing. Now that's what i call muzzle control, which is what i think a working stretcher tube gun does.
Personally i think aJRs barrel profile is more than i would use, but three barrels out of three have worked very well. The fourth, a Krieger, is to be fitted shortly and is of the same profile as he has stated. In the stretcher setup, i think that less may be more in the case of the barrel, and more may be more in the case of the tube diameter. Is there any chance of Charles Bailey coming in on this as he surely must have done a bunch of testing before he settled on what we saw in the end?
As i said before, Jeff and i have perservered with a working formula for us, it is probably not what will work best somewhere down the road and we are constantly trying other things. What i can say for sure is that if we deviate slightly from what we know, it is not always a good outcome. We keep a standard type lockup nut on the muzzle while keeping the thread diameter the diameter of the barrel muzzle as best we can. A collar that bears on the action face if possible, or on a barrel shoulder as close to the action face as possible. A T6 extruded alloy tube with very concentric properties.
With regard to actual tension, we lube the mating and rotating surfaces with a grease or antiseize and tension as firmly as the wrench allows. Fire two five shot groups and nip up the nut while the barrel is warm and elongated. Usually we get about another 1/8 turn of the nut.
Failures have been many, any type of SS tubing was a no go area for us giving POI walking and general inconsistant performance. Void filling is of little benefit and could be detrimental, though i think the coolant method has merit.
I firmly believe that a tube gun has little to do with harmonics and everything to do with structural bracing. I can only support this statement by saying that the two materials have completely different expansion rates, worlds apart heat transfer rates, yet as long as there is tension, even only a few ftlbs, the grouping and POI remains as constant as the ammuniton you feed it. If there was ever a configuration for bad harmonics, alloy and stainless steel combined together with heat will have altering lengths and thus varying tension that can do nothing but alter vibration characteristics.
Jay, all i can say is keep structural strength and muzzle control in mind, forget the harmonics side for now, and if kept simple like ours, i think success is three hours worth of machining away.
To directly answer your question, depending on barrel tennon size a 1.25 " parallel or tapering barrel to say 1" at the muzzle. Action size allowing, possibly use a 1.75 or 2" OD tube and butt up to the action face. If you can only use a 1.5" tube then a more slender profile could be used. I can't argue with Jeffs barrel profile and live in hope that one day it fails.
Tony Z.
