I successfully replaced a buggered-up cross-pinned ramp sight on my M16-4 last fall. Lucky enough to be able to drive the cross pin out with a center punch followed by a small brass drift punch. Had that not worked, the #54 bit was ready.

Replaced with a Patridge post. Base of the new sight is not a post, but is undercut and can be moved fore and aft in the old slot. Also, the new sight was not drilled for the cross-pin, so a small drop of Loc-Tite to hold it in place, then drill a #54 hole crosswise. No problem "egging" the hole as I was using a Bridgeport machine.

Most importantly, when putting in the new cross pin, I used a pair of parallel-faced pliers to insure proper pressure alignment. Whole deal took no more than 30 minutes.