Thread: 7mm RM Shhhhh

Mike,
Do not put a small thread on a button rifled barrel, especially a TrueFlite. They are the worst for opening up. You will get away with it on most Tikkas, there is usually little change in their bore diameter with even quite a bit of metal removal. But the worst muzzle bore growing we have seen has been with button rifled TrueFlites. We have seen the bore of a 300 RUM that had opened up 2 thou when turned down for a 1/2"x20 thread. Needless to say, it shot like shite! Cutting back to a section that hadn't opened up cured it immediately. Use a sensible/minimal shouldered thread size and you won't have a problem.
As to taking your can on and off, the biggy is making sure the rear bush has sufficient clearance on the outside of the barrel. This must not touch, or if you have some runout here (which you will even if your can is fitted true with the bore, almost no barrels are dead straight), then as you do the can up, it will contact the barrel differently and a tiny bit of change can seriously affect harmonics. We take properly fitted cans on and off all the time without POI shift problems. I would not shorten that barrel for your purposes. Just carry the can in your pack as you suggest, then screw it on when you get there. If the can is going to stay on permanently, then shorten the barrel by all means, but be prepared for a compromise in performance if its a magnum type cartridge requiring slow burning powder.
Short barrels and permanent cans work best with efficient cartridges like the '08's!
Greg