read mills for or has milled for.
LMT (Lewis Machine Tool) - mills for
LMT, Lauer, DS arms, PWA, Eagle, [Armalite ?], Knights Armament, And Barrett
CMT (Continental Machine Tool) - mills for
Stag, Rock River Arms, High standard, Noveske, Century, Global tactical, CLE, S & W, MGI, Wilson Tactical, Grenadier Precision
LAR- mills for
LAR, Bushmaster, Ameetec, DPMS, CMMG, Double star, Fulton Armory, Spikes tactical (CCR), Grizzly
JVP- mills for
Double Star, LRB, Charles Daly
JD Machine (Kaiser Defense) mills for
Spikes Tactical (CAK)
Mega Machine Shop (MMS) - mills for
Mega, GSE, Dalphon, POF, Alexander Arms, Spikes Tactical (BMT)
Olympic- mills for
Olympic, SGW, Tromix, Palmetto, Dalphon, Frankford, Century (old)
Sun devil was designed by TKS engineering
Sonju Industrial mills
SI Defense
Superior arms mills for
Superior, Lauer (new), Defensive Edge/CY6, Del-Ton
SMOS mills for
SMOS, Larue, custom
Aero Precision Inc. mills for
Aero Precision, Spikes Tactical (COLE), Surplus Arms & Ammo
Territorial Gunsmiths mills for
Territorial Gunsmith’s, Six Sigma Arms, CY6
Tactical Innovations mills for
Tactical Innovations, Global Tactical
Essential Arms mills their own
Hughes Precision mills their own
A O Precision (was Advanced Ordnance) mills for
FNMI, Spikes Tactical (RM)
Sabre Defense milled their own
Colt mills their own
Yankee Hills Machine mills
YHM, Spikes Tactical (MIKE)
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Not complete but pretty much what I have been able to authenticate