The M4's 14.5" barrel length reduces muzzle velocity to about 2900 ft/s. , All current M16 type rifles are designed to fire STANAG 22 mm rifle grenades from their integral flash hiders without the use of an adapter. The report of the experiment recommended that the U.S. provide the AR-15 as the standard rifle of the ARVN, but Admiral Harry Felt, then Commander in Chief, Pacific Forces, rejected the recommendations on the advice of the U.S. Most of the operating parts of the rifle were coated in Kal-Guard, a hole of 0.25 inches (6.4 mm) was drilled through the stock and buffer tube for drainage, and an O-ring was added to the end of the buffer assembly. P 292, The Complete Encyclopedia of Automatic Army Rifles, A.E. For use as an ad-hoc automatic rifle, the M16 and M16A1 could be equipped with the XM3 bipod, later standardized as the Bipod, M3 (1966) and Rifle Bipod M3 (1983). Total worldwide production of M16s is approximately 8 million, making it the most-produced firearm of its 5.56 mm caliber. The M16 internal piston action was derived from the original ArmaLite AR-10 and ArmaLite AR-15 actions. The M16 lacked a chrome-plated chamber, which allowed corrosion problems and contributed to case extraction failures (which was considered the most severe problem and required extreme measures to clear, such as inserting the cleaning-rod down the barrel and knocking the spent cartridge out).
Instead, it had a low-profile iron sight adjustable for windage and a Weaver base for mounting a scope, a precursor to the Colt and Picatinny rails. The M234 mounts on the muzzle, bayonet lug, and front sight post of the M16.
The current U.S. Army and Air Force issue M4 Carbine comes with the M68 Close Combat Optic and Back-up Iron Sight.
After a few minor modifications, the weapon gained in popularity among troops on the battlefield. After testing the AR-15 with the ammunition manufactured by Remington that Armalite and Colt recommended, the Air Force declared that the AR-15 was its 'standard model' and ordered 8,500 rifles and 8.5 million rounds.
Why settle for less when you can enjoy high performance knives at the most affordable prices?  This is the equivalent of the muzzle energy of a .22LR handgun.  Draft Standardization Agreement 4179 (STANAG 4179) was proposed to allow NATO members to easily share rifle ammunition and magazines down to the individual soldier level.
In the late 1970s, the Mk 2 Mod 0 blast suppressor was replaced by the Mk 2 blast suppressor made by Knight's Armament Company (KAC).
 Thereafter, the Army and Colt worked to make modifications to the M4s and M16A4s in order to address the problems found. In Praise of the M16 Rifle. " The M16 uses a "straight-line" recoil design, where the recoil spring is located in the stock directly behind the action, and serves the dual function of operating spring and recoil buffer.  The NATO 5.56×45mm standard ammunition produced for U.S. forces is designated M855. ", Note *: The effective range of a firearm is the maximum distance at which a weapon may be expected to be accurate and achieve the desired effect. David Crane started publishing online in 2001.  "In Fallujah, [Iraq] Marines with ACOG-equipped M16A4s created a stir by taking so many head shots that until the wounds were closely examined, some observers thought the insurgents had been executed.