Dimension to the gas port on a pistil lenght barrel?

I just picked up a 300 blk barrel with pistol length gas. I'm suspicious the gas port isn't in the right spot. Does anyone know how far it should be from the shoulder on barrel extension?

I don't need the dimension to thousandths, I think this is off by 1/8" if it is indeed off.

3.97" to C/L of hole

Thanks it appears the hole is positioned correctly. The shoulder is cut back about 1/8" too far, but I think it does no harm since the gas block I'm using is a clamp type.

Mil-Spec barrels typically have the shoulder cut back further to allow the room for the front plate for the handguard. Match barrels do not typically have this so that the gas block mates up to the shoulder.

Aha. That explains it.