There are two solutions. I've done both, and they both work well.

1. Drive out the two hardened pins holding the front sight base onto the barrel. Have your gunsmith drill and tap a 10-32 threaded hole in the bottom of the front sight back where the bayonet lug would be. Put in a set screw. Center your rear sight. Adjust the front sight back and forth until your groups are centered at 300 yards. Then apply some high strength "Geen" Loctite #290. It will wick into the space between the sight and barrel. If you ever need to remove the sight in the future, just apply 300 degree heat from a heat gun.

2. Remove front sight. Replace it with one of the newer front sight bases available from Armalite that clamp on the barrel.

The older Armalite barrel have that hideous muzzle brake that makes it impossible to pull the front sight all the way off the barrel. Buy a new flash hider from Armalite (about $24.95). Have your gunsmith turn off the old muzzle brake and thread the muzzle for the new/old flash hider.
I am doing this stuff next week to AR-10 A2 and A4 barrels. I'll send some pictures.

JCN

I will follow your suggestions. I called Armalite, they want me to mail them the upper receiver, and wait 4 weeks. Not an ideal solution for a new rifle.

Your pics would be very helpful.

Thanks,
MikeF