TM9-1276 M1, M2 & M3 Carbinesc. CARBINE, CAL. .30, M2 (fig. 3). (1) This model is almost identical with the carbine, cal. .30, Ml , except for a number of parts which have been modified, redesigned, or added, to produce a carbine which can be fired either in semiautomatic or fullautomatic position, through the use of the selector. When fired in fullautomatic, the rate of fire is approximately 750 to 775 rounds per minute. The M2 carbine can be identified by the selector (fig. 4), which projects from the left side of the receiver opposite the operating slide handle.
(2) Description of changed parts and their relative functioning are as follows (fig. 5):
(a) Hammer. Same as the Ml hammer, except that it has a milled cut in the lower right side to furnish clearance for the disconnector when assembled on the hammer pin.
(b) Sear. Same as the Ml sear, except for a raised shoulder on the top of the front end, which forms a camming surface for the disconnector when operated.
(c) Trigger housing. Same as the Ml , except that the left side of the magazine post is furnished with a retention slot, and the front face with a dismounting notch for the selector spring. (The dismounting notch leads into the top of the slot.) The right side has a milled cut for clearance of the disconnector lever.
(d) Operating slide. Same as the Ml , except for a clearance cut extending along the right-hand side of the body, and a diagonal cut at the point where the shank of the handle joins the body. The latter cut forms a cam for camming down the forward end of the disconnector lever.
(e) Magazine catch. The redesigned Ml magazine catch for the M2 has an added projection on the left end, facing forward, to act as an additional support for the 30-round magazine. This magazine catch may also be used on Ml and M1A1 carbines.
(f) Stock. A clearance cut was made in the inner right wall for clearance for the projecting right side of the disconnector. A cut was also made in the inner left wall for clearance for the selector. The bridge was cut down to the central section for clearance for the disconnector lever.
(g) Disconnector group — added parts. The disconnector pivots on the hammer pin when assembled. The rear end has a lateral projection, which bears upon the raised shoulder of the sear, when the disconnector is cam-operated by the disconnector lever for fullautomatic fire. The forward end has a projecting lug on the right side, which lies outside the trigger housing and engages and acts as a camming surface for the rear end of the disconnector lever. A spring and a plunger bearing on the receiver return the disconnector to the inoperative position, when the camming action of the lever is discontinued.
(h) Disconnector lever assembly — added parts. The disconnector lever assembly is composed of a trigger housing selector pin, disconnector lever rivet, and disconnector lever. Do not disassemble it. The pin retains the trigger housing when assembled to the receiver. The disconnector lever, riveted to a pivot on the pin, is shifted vertically, by the turning of the pin. The pin is turned by the selector. A rounded projection on the rear end of the disconnector lever operates the disconnector. A projecting toe the front end of the disconnector lever contacts the camming surface on the operating slide. An offset in the rear section provides for alignment with the slot in the disconnector.
(i) Selector group — added part. The selector is mounted to the left end of the crank pin by means of a slot in the lower forward face of the selector mating with straddle slots in the end of the pin. The selector holds the pin in position and acts as a lever for turning, throwing the disconnector lever into or out of engagement with the operating slide. A curved wire spring holds the selector in position on the pin, and in the fullautomatic or semiautomatic position when operated. The straight
front end of the spring seats into a recess in the lower rear end of the selector, and the circular rear end of the spring seats in a vertical slot in the front face of the magazine post on the left side. When assembled, the bow of the spring faces upward.
Now the person who understands what that means would also know that the Army assembled kits by which this conversion could be done. Anyone who was an Armorer up through the Viet Nam era probably had done the conversion. (Most anti-gunners were confused by the term TM and had their eyes glazed over by the third sentence.)
Given that the M2 conversion and the kit was designed and engineered to retrofit existing stocks of M1 carbines in the military it is one the easiest conversions to accomplish, if and it's a big if, you have the requisite parts.
Those conversion kits are as tightly controlled by the NFA as a functional firing machinegun, and have been since the 1950's when some were surplussed by the US Government to the civilian law enforcement market.