HELP! 03a3 front sight key.

[Doco overboard]

I just made a front sight key for a 03 rebuild barrel out of a piece of ordinary 3/16 steel rod.
I cut a long piece off, heated it up with a Mapp gas torch and filed it to shape in a very short amount of time.
I used the front sight band to trial fit the square shape and then simply shortened it to match the length of the barrel slot as needed.
Cut the excess off once you are satisfied with the shape and fit is correct.
Spot the hole for the pin and then file the relief for the pin very slightly to a shallow V shape to accept the pin which should be tapered and then dressed down to a concave shape where it protrudes through the band. (hardest part)
A 03 rebuild barrel has the same milling that is used on an A3 barrel which is the same as a CBI replacement barrel for both types.
I could have left the key longer and slightly undercut it at each end to completely fill the ends of the band. The band is longer than the slot is milled.
When you start to file the key, mark the first flat with a prick punch as they are formed to keep the other three sides square.
The whole process is not as difficult as one might think, I attached some old and new pictures from when I went through a shooter rifle and replaced the barrel.
The old key was firmly stuck in the old Avis barrel and I couldn't coax it out for re-use without destroying it.
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[browningautorifle]

I just made a front sight key

That's what I would do too but many can't so I didn't suggest...