I'll post in this thread too - this is an EXCELLENT substitute for the 5.56 75gr TAP round, which is difficult to get. Previous BT Ammo labs plus gary Robert's testing indicated that the 77gr nosler round was at least equal to the TAP round and likely slightly better when driven to 5.56 level velocities. While a .223 round, this is at 5.56 level velocities and similar to the 75gr 5.56 TAP round.
The one advantage is that this is easily obtainable and generally cheaper than the TAP round when it is available. I was surprised it did this well and think it is a perfectly valid alternative.
DT also makes an 80 gr 223 round that will fit into AR mags…tempted to get this as well, but I don't think the 3 grs would make a significant difference.