CMP/NM front sight bases are not taperpin retained, but use allen set screw so you can adjust the front sight to achieve a perfect rear sight centered for wind doping.




So I would start with pulling the FS and FSB to make sure that the gas tube was installed correctly in the FSB (look up the bottom hole in the FSB to make sure that you see the gas tube side channel centered in the gas passage channel), then when installing the FSB back on, use some pencil marks as you TDC alignment pre- live point.


As for adjusting the FSB correctly during life fire, make life simple at a indoor range with a index mark on the bottom of the FSB and shoulder.
Hence as you adjusting the set screws with a hint of loctite on them with live fire and the witness pencil lines allows you to see how far you are canting the FSB each adjustment as you are loosen one side to tighten the other.    Also to point out, I do the back set screws first to get me close, then use the front set screws to dial the FSB in with the back sight set center for a perfect zero.
Note, the rear sight centered gives you a repeat zero point to return to each match, when you start going after the rear sight to set it for wind doping during the next match.

And to point out, if you change ammo, you will need to re-zero the front sight (which is a PITA) since you have to use heat to break the loctite bond down to begin with so you don't strip the allen bolt head when loosen them once the loctite has set up, then new loctite as you readjust the FSB again.

If using the other bolt solved the problem, then take the trouble shooting the extra step.

Hence put your bolt in his carrier, and his bolt on your carrier, and try the rifle again with both combo's.

The will weed the problem down to either your bolt not head spacing correctly if your bolt on his carrier does not cycle the rifle, or the gas key leaking to the top of the carrier when his bolt on your carrier does not cycle the rifle.