I just finished my first AR build. It's a 300 blk out pistol.

KAK 9" barrel
Noveske NSR 11" rail
KAK slim Flash can
KAK lopro gas block and tube
Spikes upper
Aero stripped lower ghost gun
Spikes lower parts kit
CMC flat trigger
KAK pistol buffer tube gen 2, spring, and buffer
Primary arms reflex sight

The gas tube is against the barrel nut. Is this ok? Also when I tightin up on the buffer tube it won't allow the upper and lower to line up. I wouldn't say the buffer tube is loose but it's not tight. I plan to go to the range tomorrow morning.

Although I wouldn't guarantee it, I would think it would be fine. If you have a gas leak for a FTE/FTF that is the first place I would look. Just keep an eye on it, It should be fine.

"The gas tube is against the barrel nut. Is this ok? Also when I tightening up on the buffer tube it won't allow the upper and lower to line up. I wouldn't say the buffer tube is loose but it's not tight. I plan to go to the range tomorrow morning. "

t:  So long at the aft end of the gas tube slides in and out of the bolt carrier key, its no problem if it touches the barrel nut.  As for your buffer tube, it should only screw into the lower receiver far enough to engage the edge of the buffer retainer.  Then the tube is locked in place with a castle nut.  It should not be loose at all.  Refer to the various tutorials and videos for pics of the parts in question. - CW

Thanks for the replies.

Tim

That pistol tube takes a castle nut?

 Pardon my ignorance, I've never considered building a AR15 pistol.  After checking further, I learn that some pistol receiver extensions employ a castle nut and some don't.  Those that don't appear to just screw down tight, with a shoulder bearing against the end plate and threads that extend exactly enough to catch the little spring-loaded buffer retainer.  Since there is no provision for a buttstock (the extension is a simple round tube), there is no need to orient the angular position of the extension.  

In view of the problem cited by the OP, I'm guessing he has one of the types that requires a milspec end plate and castle nut to fix the threads at the right depth to properly engage the retainer. - CW

My KAK pistol buffer tube was about 1/16" too long so I had to grind it down until I could close the upper and lower together

This is what I will probably do.

Tim