I was wondering how tight the fit needs to be with the gas tube and carrier key. I had

to polish my tube down a little to fit inside the key. It wasn't an alignment problem the

diameter of the mushroomed end was larger then the inside diameter of the carrier

key. I check it with some calipers and there was about a .015 difference. it fits nicely

now with little to no play between the two.  but i have not shot the gun yet it's a 6.8 spc

caliber. Has anybody ever ran into this problem? Am I going to have cycling problems?

If so I want to order a new tube as soon as possible, also has anybody ever had to tap

in a tube into the gas block? I have a new PRI low pro and the fit between the tube

and block where super tight it required me to have to tap in with a rubber mallet. Is

this normal?

Tight tubes at the block/FSB are a good thing as long as it is aligned properly with the port.  Hard to measure for sure but the hole in the FSB is much larger.

As far as the fit of the other end into the key, it should not bind.  It needs to "float" in the hole in the upper receiver.  They will wear in, then last forever as long as they are not abused.  

The fit of the key to the carrier could allow for leakage.  I used a bit of Permatex Form a Gasket on a friend's build 15 years ago as he had a poor fit.  This stuff is an automotive product that is solvent resistant, well, everything but alcohol.  It worked perfectly.