The M4 Survival Rifle was developed during WWII as part of the survival gear stored under the seat of American military aircraft, to give downed aircrew a survival weapon for foraging wild game for food.
The M4 was developed from the Harrington & Richardson bolt-action M265 sporting rifle, adapted to a sheet metal frame with telescoping wire butt stock, a 14-inch detachable barrel chambered for .22 Hornet and the 4 shot detachable box magazine of the Savage Stevens M23D .22 Hornet sporting rifle. The M4 weighs approximatey four lbs and with the barrel detached and telescopic stock closed maeks a ~ 14 inch overall package.
Due to the possible use of the M4 by downed aircrew as a combat weapon, military-issue ammunition in .22 Hornet is loaded with full metal jacket bullets to comply with the Hague convention barring the use of expanding bullets in warfare.
In the 1950s the M4 was supplanted by the M6 Aircrew Survival Weapon and the M4 was phased out along with the decommissioning of the aircraft containing the M4 as part of their survival package. The ArmaLite AR-5 was approved as a replacement for the M4 but no significant quantities of the AR5 were procured, as there were significant numbers of M4s and M6s in inventory to meet USAF needs.
The US National Park Service was issued some of these surplus M4s for park rangers in the 1960s.