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M4 carbine
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<p>The M4 carbine (officially Carbine, Caliber 5.56 mm, M4) is a <a href="/facts/5.56%25C3%259745mm_NATO/eT9ENFzY">5.56×45mm NATO</a> <a href="/facts/Assault_rifle/H2DXHauQ">assault rifle</a> developed in the United States during the 1980s. It is a shortened version of the <a href="/facts/M16A2_rifle/kre1Wcpd">M16A2</a> assault rifle. The M4 is extensively used by the <a href="/facts/United_States_Armed_Forces/NHVsU9Id">US military</a>, with decisions to largely replace the M16 rifle in <a href="/facts/United_States_Army/WACWBEK9">US Army</a> (starting 2010) and <a href="/facts/United_States_Marine_Corps/J8JDlJG2">US Marine Corps</a> (starting 2016) combat units as the primary <a href="/facts/Infantry/QAHDDQtk">infantry</a> weapon and <a href="/facts/Service_rifle/CejsNRy7">service rifle</a>. The M4 has been adopted by over 60 countries worldwide, and has been described as "one of the defining firearms of the 21st century." </p><p>Since its adoption in 1994, the M4 has undergone over 90 modifications to improve the weapon's <a href="/facts/Adaptability/uhdgJxKk">adaptability</a>, <a href="/facts/Ergonomics/prAcGtDW">ergonomics</a> and <a href="/facts/Modularity/mptqhanB">modularity</a>, including: the M4A1, which possesses a thicker barrel and a replacement of the <a href="/facts/Burst_mode_(weapons)/AbDboJ6q">burst-fire</a> control group with a <a href="/facts/Automatic_firearm/al4qSyv2">fully automatic</a> one; the <a href="/facts/SOPMOD/QWbIRpBU">SOPMOD</a>, an accessory kit containing optical attachments; and the underbarrel weapons such as <a href="/facts/M203_grenade_launcher/drnn8N0k">M203</a> and <a href="/facts/M320_Grenade_Launcher_Module/H8dAYSMv">M320</a> <a href="/facts/Grenade_launcher/TjWnnf9b">grenade launchers</a> to the <a href="/facts/Knight%2527s_Armament_Company_Masterkey/Ln0Hy2RE">Masterkey</a> and <a href="/facts/M26_Modular_Accessory_Shotgun_System/dVhcXJBV">M26-MASS</a> <a href="/facts/Shotgun/tGxz1bqj">shotguns</a>. </p><p>In April 2022, the U.S. Army selected the <a href="/facts/XM7_rifle/JgluFuXk">XM7 rifle</a>, a variant of <a href="/facts/SIG_MCX_Spear/AvatvUYC">SIG MCX Spear</a>, as the winner of the <a href="/facts/Next_Generation_Squad_Weapon_Program/WJqvw04B">Next Generation Squad Weapon Program</a> to replace the M16/M4. </p>