I had a similar issue with mine (at least i think we are talking about the same thing.) this sounds nuts but what I did was simply JB weld the tube to the front barrel ring. It took about 2 drops and I made sure it was good and hidden between the ring and the tube. Now, I can still remove the tube by removing the front barrel ring.
If you can show a pic or two it would help. It sounds like a crap job but it has been that way for more than a couple of years without any movement and you cannot even see the difference.
If you consider this option, just make sure that you position the barrel ring exactly where it needs to be so that the tube is snugly in place when you put it on. Then make sure you have some cotton swabs and alcohol to clean up any jb weld that might end up where you can see it.