Bristo,
X-Terminator is one of my favorites for lighter .223/5.56 bullets. At about 60 grain bullets I switch to TAC, H4895, Varget, 8208 XBR, or other slower powders.
Here are some of my more accurate loads with X-Term. Most are near, at, or slightly over max loads. Work up safely.
AR, 16" barrel, 1:9 twist
50 gr. Nosler BT-Varmint - 26.3 gr. X-Term, Rem 7-1/2 primer, 2.255" OAL, 3,160 fps (This is over Western Powders SAAMI max, but under 5.56 Nato Max)
55 gr. Hornady FMJ or Soft Point - 25 gr. X-Term, Rem 7-1/2 primer, 2.23" OAL. 3,000 fps
AR 18" barrel, 1:8 twist"
55 gr. Hornady FMJ or Soft Point, 24.6 gr. X-Term, Rem 7-1/2, 2.20" OAL, 3,000 fps
69 gr, Sierra MK HPBT, 24.7 gr. X-Term, Rem 7-1/2, 2.255" OAL, 2,900 fps
