You cannot expect the pin holes in the front sight to match up to any barrel but the one it came off of.
The front sight is installed on the barrel, held square in a jig, then drilled for the taper pin. The barrel and front sight are then an assembly, and the front sight is not designed to be used on another barrel.
I forgot about that. I was thinking of clamp on gas blocks for some reason.
If you want to replace the gas block, you can do so with a clamp on style gas block. Swapping them wouldn't be an option in this case as -k- as pointed out.
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