barrel installation question

[Txs]

I'm familiar with the basic AR barrel removal/installation procedures, but I've never actually done it.

What procedure must be followed to insure the new barrel mounts within acceptable tolerance of mechanical zero?

[sgtlmj]

At the factory they torque the bbl nut between 30-80 ft/lbs and then use a long steel gauge to ensure the top of the carry handle is aligned to the front sight.

[Iraqgunz]

Here are a few hints.

1. When installing the barrel retaining nut I tighten the nut down (work the threads) 2 times. The third time is when I do it for real. Also, you are well advised to use a high temp anti-seize compound.

2. The proper torque according to the military TM w/ change 8 is 30 ft./lbs and up to 80 ft./lbs (though I personally have not seen it go that far). If the gas tube is slightly tweaked in the upper receiver afterwards, don't worry. With a flat tip screw driver and minimal tweaking you can usually get it centered.

3. I use an old gas tube that is cut down about 5 in. long to help make sure that everything is straight.

4. Never re-use any roll pins, split pins or taper pins unless absolutely necessary. Spend the money on new ones.