Mind you, I'm not saying it can't
be done. But for the cost of a new tube, it just seems impractical to me. Normally you would replace the tube when the "mushroom" wears off at the receiver and causes gas leakage. (Due to misalignment of the tube & gas key...)
J.D. is correct in that, it is no guarantee
that you will have cycling issues however. But if you cut it off and the gun starts having problems, the worst you are out is the cost of a new tube, assuming you get it aligned correctly (the bends mentioned above) and don't damage the gas key.
Thinking outside the box, if I HAD to shorten a tube (SHTF) -- I can only think of three possible solutions, and all three involve the use of a TIG welder (not found in most peoples garage) seeing as how you are working with a stainless steel tube. I actually had a fourth idea, but don't know how I would accomplish it. JD
: Can we compare notes? How would you go about doing the mod? I'm always up for learning new things.
It's up to you if you want to cut off the end of the long tube and give it a try. I'm sure there are a LOT of folks here that would be interested in hearing the results, if you wanted to do some experimenting. If not - no harm, no foul.