Just recently picked up my 5th Mark IV, a 4.5x14x50 M1 Illuminated TMR and stuck it on a FN A1.It's makes a great combination for the 308.For precision work dialing in and knowing your load is the only way to go.

The factory bdc's are good but are made for general cartidge ballistics,it may be close for your particular load or may not, you are going to have to shoot at various ranges to see no matter what.
I have been messing around with the Nikon5.5x16.5 BDC reticle on a Cooper 243 Win and out to 500 yards it works quite well, the 1st circle is on at 300 while I skip the second and use the third circle for 500 yards, which prints groups 3 inches low.I picked up 2 new modelNikon 5x20x42 BDC's for future projects. Good luck on your new rifle, I just may have to knock the dust off my 6mmx284 now that I think of it.