There are three M1 sniper's rifles: (1) the M1C, (2) the M1D, and the MC-1 (M1952). The M1C and M1D sniper's rifles were developed as the M1E7 and M1E8 by Springfield Armory during 1943-1944. A very few M1C rifles saw combat in the closing days of World War 2. The M1D did not see action until the Korean War.
The M81, M82, and M84 optical sights were roughly the same size, weight, and construction. The principal difference was in the windage and elevation knobs and the reticles of the scopes. The M81 scope had a vertical post; the M82 had a cross-hair; the M84 had a vertical post and cross-hair that was used to eliminate 'canting' of the rifle. These scopes were about 2.2-power optics with rubber eye cups on the back and extendable sun shades on the front. Tube diameter was about 3/4 inch. The scopes themselves were not cutting edge technolgy even for the 1940's. They are only useful out to about 600 yards, but they are deadly in the hands of a good sniper.
The M1C rifle uses the Griffin & Howe mounting rail and throw lever mount. The mounting rail requies drilling and tapping the M1 receiver for three socket head cap screws and drilling two holes for taper pins. Conversion of the receiver is difficult if it has been heat treated; the surface hardness of the receiver is difficult to drill through. I did a conversion of a standard M1, but we used EDM to do the screw and pin holes.
According to what I have read, only 4,000 M1C rifles were manufactured before the end of WW2. About 1952-1953 some 2,000 of these rifles were reconverted to standard M1's by removing the scope rails and plugging the screw and pin holes! No one knows why Springfield Armory did this. In any case, the M1C rifle is rare and commands a healthy price tag.
A rarer variant of the M1C is the MC-1 (or M1952) sniper's rifle. This rifle was a conversion of the standard M1C by the United States Marine Corps. Whether all M1C rifles in USMC inventory were updated to the M1952 standard is not known. Most likely both M1C and MC-1 (M1952) rifles remained in service with the Corps until replaced by the M40 bolt action sniper's rifle beginning in 1966-1967.
To build the MC-1 (M1952), the M81, M82, or M84 scope was discarded along with its rings and throw lever rail. A longer Griffin & Howe throw lever rail was fitted with 1-inch diameter rings. The 4-power Stith Bear Cub sight, manufactured by Kollmorgen Instrument Co., was mounted. Unlike the earlier M81, M82, or M84 scopes, the Bear Cub scope did not have and extendable sun shield or rubber eye cup. The Bear Cub scope had very large windage and elevation knobs with audible click adjustments.
The M1D is the most common version of the M1 sniper's rifle. This rifle was designed for build-up by ordnance shops. The standard M1 barrel was replaced by the M1D barrel. This barrel was ground down at the rear, had a barrel block pressed onto the end, and the block was pinned in place. The block itself was tapped for a single machine screw. The scope mount was a hinged clam-shell type that accepted either the M81, M82, of M84 scopes. The mount had an indexing shoulder and a single, not detachable screw topped with a large knob. The wooden rear hand guard was shortened to accomodate the barrel block. All other parts of the standard M1 continued in-use.
The M1C, M1D, and MC-1 (M1952) sniper's rifles had several accessories. The rifles were issued with the M2 flash hider (a cone-shaped device that slid over the end of the barrel and clamped onto the bayonet stud on the gas cyliner). After the Korean War, the M2 flash hider was superseded by the T37 flash suppressor. The T37 replaces the gas cylinder lock, which is incorporated into the five-pronged suppressor. The T37 is more efficient than the M2; instead of hiding the muzzle flash from the sniper at night, the T37 broke-up the muzzle flash to help hide the sniper from the enemy.
Because the M1 rifle is loaded with an 8-round enbloc clip through the top of the action, the sights of the sniper rifles were offset to the left to allow for loading. In order to allow the use of both iron and optical sights, Garand sniper rifles were fitted with a leather lace-on cheekpiece. The cheekpiece allowed the sniper to get a good stock or cheek weld on the stock while giving him the opportunity to use either iron or optical sights. The cheekpiece itself had felt inserts for adjustment to fit the sniper and was attached by two brass screws and leather lacing to the stock.
The standard sling issued with the Garand sniper's rifles was the M1907 leather sling or the M1 web sling. Because the leather sling required a lot of maintenance in the field to keep it from deteriorating, the web sling became the dominant sling.
All standard and sniper versions of the Garand carried a cleaning kit in the stock beneath a hinged door in the butt plate. This kit consided of a small plastic pot of rifle grease (Lubriplate) for the bolt lugs, operating rod cam, and other areas needing lubricating grease. There was the M10 cleaning rod that consisted of the head. The M10 head had a screwdriver to tighten the various fasteners of the rifle and as a disassembly/assembly tool for the bolt's extractor and ejector spring and plunger. The rod itself was in four screw-on sections and had a slotted tip, a plastic spacer to protect the muzzle from damage by the handle, and a copper bore brush. The brush, tip, and four sections of cleaning rod were contained in a cloth pouch that was inserted into the two bored-out holes in the stock.