Bushmaster XM15E2 Shortys (16")wear Trijicon ACOG-1 in 4x.
H&K SL-7 is topped with a Burris compact 3-9, which stays pretty much on 3x.
Valmet M62S is occasionally topped with an old Weaver Wideview in 2-1/2X, but the 76FS is iron only.
Colt 9mm Carbines are iron.
Colt HBAR uses Colt 4x w/ BDC. Smith Ent. M-14NM uses an old Leatherwood ART-II, 3-9x, with the cam rangefinder/BDC. H&K 91 is a Kahles zf69, 6x BDC.
Some of these aren't very practical as tactical carbines although the respective mfgs would argue the marketing point of their short-barreled versions of like or similar design.