6.5 Grendel
I measured 274.8 grains for a round with a 130gr bullet.
I measured 271.8 gr for a round with a 123 gr bullet.
I didn't have any 223 to compare it to.
The 6.5 G comes in at about 25 cartridges per pound. 5.56 x 45 M855 comes in at at about 50 per pound.