I was shooting my new AR6450 a couple a days ago at the range, after about 200 rounds
the handguards started to rotate. I thought this was wierd so I took off the handgaurds and
noticed the barrel nut was loose. Since there isn't a gas tube to lock the nut I guess it decided to loosen up after a few heat cycles. This range doesn't allow rapid fire so that wasn't a contributing factor (3 seconds between shots).

I took the upper to a local vendor C&S Mettal-Workes and they tightened for me. I also had them put a short piece of gas tube in the FSB so that the front of the guards would rotate either.

It's fixed now but this really blows....spend big bucks on a new firearm and then have it
need work done to it after a few hundred rounds. I called Colt and told them what happended for what good that will do. It reminds me of owning a new car....

Anybody else have this happen to you ????

I put a dummy gas tube in my dedicated upper to solve this problem.

If you torque that barrel nut to about 50 ft/lbs, it shouldnt come loose to begin with.

Colt doesn't drill the upper for a tube so a full length tube won't fit. A stub will fit in the FSB so at least the handguard support won't rotate. The barrel nut is torqued on there now so this shouldn't happen again.