R6600
Serial numbers picks up were the SP1 left off, produced 1985-1990. Features are as such:
CM upper forge code, big hole slab side lower, no sear block, no auto sear cut in upper, small pin hammer/trigger pins, modern small forward assist, SP1 bolt carrier, bolt marked MPC with a space between the M and the P, blue extractor buffer, AR-15 A2 HBAR SPORTER, lower roll marked COLT’S FIREARM DIVISION, barrel stamped C MP 5.56 NATO 1/7 HBAR, peel washer, A2 furniture, bayo lug
Not going to list features of each example, unless they are different then indicated above. The Delta HBAR, R6600DH was introduced in 1987.
215677 appeared in the May 1986 issue of American Rifleman
22151X
2293XX made in June of 1988
233978
245018
249256 this is a Delta H-BAR, as in R6600DH, white label box
R6601
1990
In general these have the following features:
CM or CMB upper forge code, modern small forward assist, roll marked SPORTER MATCH HBAR, SPORTER bolt carrier, bolt marked MPC with a space between the M and the P, blue extractor buffer, barrel stamped C MP 5.56 NATO 1/7 HBAR, peel washer, A2 furniture, no bayo lug
247401 CM upper forge code, big hole slab side lower, no sear block, no auto sear cut in upper, small pin hammer/trigger pins, modern small forward assist, SP1 bolt carrier, bolt marked MPC with a space between the M and the P, blue extractor buffer, AR-15 A2 HBAR SPORTER, lower roll marked COLT’S FIREARM DIVISION, barrel stamped C MP 5.56 NATO 1/7 HBAR, peel washer, A2 furniture, this is a R6600K, no bayonet lug, with a .22 conversion kit, built in 1990
2497XX CM upper forge code, big pin slab lower with no sear block, modern small forward assist, roll marked SPORTER MATCH HBAR, SPORTER bolt carrier, bolt marked MPC with a space between the M and the P, blue extractor buffer, barrel stamped C MP 5.56 NATO 1/7 HBAR, peel washer, A2 furniture, no bayo lug, small hammer/trigger pin holes, roll marked COLT'S MFG, blue label 6601 box, purchased in June of 1990
MH 001001 A2 lower, big hole pivot pin, no sear block
MH 006600 and up have large trigger/hammer pins
MH 007657 slab lower with no sear block, CM upper, roll marked COLT'S MFG, 1990 manufacture
MH 010063 slab lower with no sear block, roll marked COLT'S MFG
1991
MH 013495 A2 lower with mag fense, big hole pivot pin, sear block pinned on both side, CM upper, made in 1991
MH 029XXX slab side lower, big pivot pin, sear block appears to be pinned in on both sides (with two on the left), looks like it has a SPII upper on it
MH 0295XX slab side lower, big pivot pin, sear block appears to be pinned in on both sides (with two on the left), made in 1991
MH 031037 CM upper forge code, slab side lower, big pivot pin, sear block appears to be pinned in on both sides, roll marked COLT'S MFG
1992
MH 04242X A2 lower with mag fense, big hole pivot pin, sear block pinned on right side, roll marked, COLT'S MFG
1993-1994
MH 0573XX CM upper forge code, mag fenced lower, small pivot pin hole, weep hole drilled, marked COLT'S MFG CO. INC., sear block pinned in on right side
MH 0649XX mag fenced lower, small pivot pin hole, weep hole drilled, bolt marked MPC and carrier has a "C" , was made in Sept. 1993 according to Colt
MH 074104 CMB upper forge code, mag fenced lower, small pivot pin hole, weep hole drilled?, marked COLT'S MFG CO. INC., sear block pinned in on right side
MH 089612 mag fenced lower, small pivot pin hole, weep hole not drilled, marked COLT'S MFG CO. INC., sear block pinned in on both sides
MH 09XXXX CMB upper forge code mag fenced lower, small pivot pin hole, weep hole not drilled, marked COLT'S MFG CO. INC., sear block pinned in on both sides, Vietnam Tribute engraved rifle
MT6601
1994-
Same as R6601 less flash hider, and now roll marked MATCH TARGET MATCH HBAR
CMH 001002
CMH 00177X Gray finish, CMB upper forge code, mag fenced lower, small pivot pin hole, weep hole not drilled, marked COLT'S MFG CO. INC., sear block pinned in on both sides
CMH 003084 purchased this as a complete lower assy from CDNN in 05/08/96 for $289.99, don't recall the features
CMH 026653 appears to be black, small pivot pin hole, weep hole not drilled?, marked COLT'S MFG CO. INC., no pinned in sear block
CMH 031231 black finish, small pivot pin hole, weep hole not drilled, marked COLT'S MFG CO. INC., no pinned in sear block, purchased this as a stripped lower from R-GUNS,
CMH 035XXX black finish, small pivot pin hole, marked COLT'S MFG CO. INC, 04/00
CMH 041298 black finish, small pivot pin hole, weep hole not drilled, marked COLT'S MFG CO. INC., no pinned in sear block, this one has a brake making it a MT6601C
1995- LEO AR-15 HBAR AR6601
These are the same as the MT6601 but have a flash hider and are roll marked AR-15 MATCH HBAR
LMH 0015XX black finish, C and A upper forge code, small pivot pin hole, weep hole not drilled, marked COLT'S MFG CO. INC., no pinned in sear block,
LHM 001XXX black finish, no pinned in sear black, marked COLT'S MFG CO. INC, suspected 2001 production