The M4 is the carbine variant of the AR-15 adopted by the United States Military, derived from the M16 assault rifle adopted by the United States. Manufacturers have changed over time in light of military contracts. The first M4s were made by Colt, and later also supplied by Fabrique Nationale.

Variants[edit | edit source]

M4[edit | edit source]

Introduced in 1994, this model features a collapsible stock, a carbine-length gas system, shorter handguards, and a 14.5 inch barrel with a notch to accommodate the M203 underbarrel mounted grenade launcher. The barrel assembly features M4 feed ramps; whereas the feed ramps in a rifle are angled at 45 degrees, the M4 feed ramps are longer and slightly steeper (52 degrees) to enhance reliability in the carbine system. The front sight block is also slightly taller ("F" marked). The FCG has three positions: SAFE, SEMI, and BURST. The earliest models featured an A2 upper receiver; flat-top models have replaced them.

M4A1[edit | edit source]

Same as the M4, except for the FCG, which has AUTO parts in place of the BURST FCG. The M4A1 also has the heavier SOCOM profile barrel, as opposed to the Government profile barrel used on the M4. Most M4A1 models were converted over from M4s. They were almost supplied entirely by Remington, but Colt protested the decision and won over 88 million USD to continue the contract, which is still being situated with the US government, with the goal of allowing more companies to provide M4A1s.[1] They are now also supplied by Fabrique Nationale.

CQBR[edit | edit source]

Main article: Close Quarters Battle Receiver

Replacement upper receiver for the M4A1 with 10.3 in (26 cm) barrel.

FN-15 Military Collector M4[edit | edit source]

A civilian marketed semi automatic M4A1 on offer by Fabrique Nationale, sporting changes such as the removal of the select fire capability and a 16 inch barrel to comply with US firearms laws. [2]

Trivia[edit | edit source]

  • The M4 name is essentially a sequential continuation of the designations of military carbines which started with the M1 carbine.
  • Colloquially, M4 has come to mean "shortened AR-15", with many non-Colt manufactured M4 rifles (Such as the Bushmaster M4) becoming known as "M4-geries".
  • Colt long held a trademark for the M4 name. In spite of this, Bushmaster, Heckler & Koch and several other companies producing AR-15 platform rifles still developed products bearing the M4 name. In 2007, Colt sued Bushmaster over the supposed infringement. The ruling was in favor of Bushmaster, and set the further precedent that military designations for weapon systems cannot be trademarked. [3]
    • This comes after a dispute between Colt and the US military, where Colt raised a case against the military for releasing proprietary information about the M16 in 1997. The military made an Addendum to their contract, and listed them as the sole supplier of M4s until 2011.
    • Adding to Colt's loss in the case, McCarthy § 20:56 ruled that if a product becomes a generic name for a good or service, the registration of the trademark can be withdrawn at any time.
    • COLT DEFENSE LLC v. BUSHMASTER FIREARMS, INC. is in long keeping with Colt's extremely protective legal team, as Samuel Colt himself was diligent in keeping his designs proprietary to Colt. At one point in time, this even earned him a reprimanding from the US government for stunting the development of the revolver, which the government argued could have been used to further US military technology had he not been so protective.

External Links[edit | edit source]

References[edit | edit source]

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