So I got my barrel today, and I decide to install it on my RRA upper.

I coat the barrel extension with Moly grease and start to work it into the upper.  It's extremely tight, so it requires quite a bit of tapping.  I had tried to line the little nub up perfectly, but I was off by the tiniest amount...just enough that the nub catches on the receiver and won't slip into the hole.

So, I try twisting the barrel (upper is in a action block in a vise), but I simply can't put enough torque on it to line the nub up with the slot.  This barrel is REALLY tight in the upper receiver.  

I've tried 2 different strap wrenches (different sizes), but neither will catch on the barrel.  They both slip rather easily.

So, I'd like to either try to remove the barrel and start over or twist the thing so I can continue to tap it into place.  Ideas?

Should the upper be this tight?  Maybe there's a problem there?  It's a Colt 20" HBAR barrel and a RRA receiver.

I've built 3 other uppers, but I don't ever remember the barrel/receiver fit being so tight.

For what it is worth my bushmaster barrel in RRA upper is VERY tight, similar to yours.  It had to be perfectly straight to go in but the fit is so perfect once in it seems like you could just hand tighten the barrel nut and it would still function fine.  (of course I would still tighten it down to spec.)  I really like the snug fit but mine does not sound as bad as yours.

So, do you think I should just install the barrel nut and let it position the barrel into place?  I was worried that I would just make things worse.

[Edit]THANK YOU JUSTY!

If you look at the post and the edit times, you'll see that it took all of about 3 minutes to perform your solution.  AND IT WORKED!  

I appreciate it.  You saved me a lot of trouble.

cant you use a pair of pliers on the barrel to wiggle it back and forth out of the receiver?

Any marks you leave will most likely be covered by the handguard.

I had the same issue with a Bushmaster barrel and RRA upper, At least as far as it being really tight. I simply lined up the nib with the slot and then used a wooden mallet to gently tap it home. Worked fine.

use a wooden dowel through the receiver to tap the barrel back out of the receiver and start over.

I've never done this so my suggestion might be way out in left-field.

Would freezing the barrell shrink it just a little bit so it would fit in easier?