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M-4 Bayonet

In May of 1944 the M-4 bayonet was standardized for use with the M-1 Carbine, adopted in 1941 to be carried as a substitute for the M-1911A1 automatic pistol by certain officers and many specialized soldiers such as mortar or machine gun crews or paratroopers.

PFC Richard N. Martin overlooking the Naktong River, South Korea, 19 August 1950.  Fixed M-4 bayonet seen behind canteen -- M8A1 scabbard on leg.
PFC Richard N. Martin overlooking the Naktong River, South Korea, 19 August 1950. Fixed M-4 bayonet seen behind canteen -- M8A1 scabbard on leg.

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M-4 Bayonet Description

M-4 Bayonet with Plastic Grips (1954 and later)
M-4 Bayonet with Plastic Grips (1954 and later).

Although first produced during World War II, the M-4 Bayonet was little used in the war for its intended purpose. Few Carbines were available with the bayonet adapter until the very end of WW II so the M-4 was primarily used as a general purpose fighting knife in that conflict.

The blade of the M-4 Bayonet is 6 3/4 inches long and the overall length is 11 3/4 inches. The M-4 bayonet locks into place on the carbine muzzle by two spring-loaded attaching lock levers on the rear end of the hilt. It is released by simultaneously pressing the two lock levers and pulling forward. Early production M-4 bayonets (World War II) had brown leather grips (stacked washers), later replaced by black plastic grips (starting in 1954). The photo to the right shows the M4 bayonet with leather grips, used as a fighting knife. Many other small changes took place during the production lifetime of the M-4 bayonet.

There are no markings on the blade itself. The mark "US M4" will be stamped underneath the cross-guard along with the manufacturer marking: (Aerial [ACC], AKI, Bren-Dan, Camillus, Case, Conetta, Eickhorn, Horster, Imperial, Kiffe, Kinfolks [KI], Kongsberg, Pal Blade, Republic of Korea [ROK], SI, TOD, Turner [TMN], Utica and possibly others. All metal parts were dark grey Parkerized although a brief early production period was blued.

M4 bayonet with leather grips, used as a fighting knife

M-4 bayonet fixed to M2 carbine, 1945 photo
M-4 bayonet fixed to M2 automatic carbine, 1945 photo.

Scabbard for the M-4 Bayonet

M8A1 Scabbard for M-4, M-5, M-6, and M-7 bayonet
M8A1 Scabbard for M-4, M-5, M-6, and M-7 bayonet.

There are two variations of this scabbard, both with an olive drab fiberglass body with steel throat. The early version, designated M8, has only a belt loop, no hook. The M8A1 retains the general look and can be slipped over a belt, but also has the M-1910 bent wire hook available. The model is stamped "US M8" or "US M8A1" on the flat steel part along with manufacturer initials. This sheath is correct for all post-war US bayonets including the M-4, M-5, M-6, and M-7. It was also used with the M-3 Fighting Knife.

The "Scabbard, Bayonet Knife, M8A1" is assigned NSN 1095-00-508-0339. It has been replaced by the black "Bayonet-knife scabbard M10", NSN 1095-00-223-7164. Huge numbers of the M8A1 were produced and surplused and are widely available.

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