I guess the FAQ on their website is not updated
What bullet was used to calibrate the ACOG scopes?
The TA01, TA11, & TA31 (.223) were designed for the 5.56mm, 20 inch barrel, 55 grain bullet, and M16/AR15 carry handle mount. The TA01B & TA11C(.308) were designed for the 7.62mm, 20 inch barrel, 168 grain bullet, and M16/AR15 carry handle mount. The TA01NSN was designed specifically for the US Special Operations Command SOPMOD M4 Carbine. To meet their requirements, the reticle bullet drop compensator and range finding stadia lines were based on the trajectory of the 62 grain bullet from a 14.5 inch barrel, flattop mount (Picatinny rail Mil.Std.1913).
anyway this FAQ is interesting
Does bullet weight and/or barrel length effect the reticle bullet drop compensator and range finding stadia lines?
The real issue is not the bullet weight or barrel length, but muzzle velocity, ballistic coefficient, and the distance from height above bore. The difference in trajectory from bullet to bullet or barrel to barrel is usually less than the MOA thickness of the stadia lines.
so, as long as the NSN-308 was designed for flat top receivers you should be GTG