[If the brass is headstamped as NATO ammo, it probably is loaded with Ramshot TAC. NATO started to specify this powder a few years back. It's extremely temperature stable and produces same velocities at extreme temps. It also burns exceptionally clean and exceptionally cool which makes the gas system operational for longer periods of time. The normal loading for it is 26.7 grs under the green bullets.]
Just got back into reloading after a 30 year hiatus. Loading for AR-15. using Ramshot TAC, and loving it. Took a little while to get the powder thrower all lubed up with the graphite in the powder, but all is well now. I am also using the TAC for 300 Savage and in my 30-06. nice stuff. For the .223 I am using 24.7 gr under Sierra 55gr BT/HP Amazing accuracy.