Originally Posted By shultz:
The pin isn't really needed for a 9mm barrel unless your's has feed ramp that needs indexing, or in your case an FSB. Most 9mm barrels have a conical feed cone thats not indexed.

The issue you'll run into removing the index pin is when you torque the barrel nut, the barrel will want to turn with it.

If your lucky, the FSB cant is a little right. Shave the index pin or the index pin slot until your happy with alignment. As you torque the barrel nut down, the barrel will pull with the nut and stop at your alignment adjustment.

If not, I'd shave the index pin then make a little shim to fill the gap on the opposite side so the barrel can't move when you torque down the barrel nut.

Originally Posted By IdahoPCCinc:
Is the barrel from a known manufacturer ??
If you know where it's from, I would contact them and see what they say about it.


That being said, you could try to pull the barrel pin and try to align it as you tighten the barrel nut.
I would clamp the barrel in a barrel vise, with the A2 sight straight up.
Put a 2in or 3in long 5/64th (.075-.078 dia) pin through the gas tube roll pin hole to use as a visual alignment tool.
Side the upper receiver onto the barrel, and begin to align it as you tighten the barrel nut.
This way you'll have a flat plane to look at from the rear of the upper so you can compare the pin to the top portion of the upper receiver (assuming you're using a flat top upper).
A long straight edge against the side of the upper receiver could also work to align the receiver to the sight.
Just check both sides and find the dimension to each side of the sight.
It should also work if using a carry handle (A1/A2) upper receiver.



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Originally Posted By chevrofreak:
If you pull or cut the pin and clamp the barrel in a vise, as you tighten the nut it should help prevent the barrel from turning in the receiver once you have it lined up.