M3 Grease Gun Patent Poster

The suppressed M3 submachine gun was immensely popular with OSS operatives during World War II. Development began in mid-1943 and by May 1944 an order for 1,000 suppressors was placed by the OSS with the High Standard Manufacturing Company. Once the weapons were made available, they were shipped to OSS detachments worldwide. At least forty were used in the fight for Okinawa, to high praise and great effect. Within months an additional order for 4,000 more suppressors was placed as everyone who could get one, wanted one.

The M3 submachine gun was commonly referred to as a “grease gun” due to its resemblance to a mechanic’s tool. It was far cheaper and easier to produce from stamped metal than the Thompson submachine guns which it was intended to replace. The M3 had no bolt or cocking lever. Instead, the operator opened the ejection port and pushed the bolt back into the open position with his finger. It made for an excellent suppressor platform due to its subsonic .45 ACP ammunition and slow rate of fully automatic fire.

At least one suppressed M3 submachine gun in 9mm was produced by engineers at High Standard, but its performance was considered unsatisfactory. It remained in the OSS inventory at war’s end. Allegedly that project received another look in the 1960s, likely by the CIA.

The suppressed M3 continued to see service long after World War II ended. MACV SOG legends John Plaster and  Jerry “Mad Dog” Shriver both carried them during their years in Vietnam.

Now available is the illustration accompanying the original patent application for the M3 submachine gun, described here as a "FIrearm Construction" by inventors Frederick Sampson and George Hyde. The patent application was submitted in May 1944 and awarded in July 1946. 

These posters are 11" by 17" and printed on heavy 65-lb paper for a memorable texture and durability.  All printed posters are sourced from a small, local family-owned business. Each poster is shipped in a 12" x 2" cardboard shipping tube.