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Would you stake your life, right now, on the condition of your equipment?
NEWS | May 10, 2023

M4 and M16 Series Rifles: Only You Can Avoid a Cook Off

BLUF: Continuously firing a weapon in excess of the sustained rate of fire can overheat the barrel and cause a cook off.

M4 carbine
Photo by Davide Dalla Massara

Soldiers, if you think only machine gun rounds cook off, you’re wrong. A cook off can happen to your rifle if the allowable sustained rate of fire is exceeded by rapid and continuous fire, causing the barrel to overheat.
A live round in a hot chamber can detonate (cook off) in as few as ten (10) seconds. That means you need to remove it in under ten (10) seconds if you’ve exceeded the sustained rate of fire. If the round can’t be removed, then remove the magazine and let the weapon cool down for 15 minutes. Keep the weapon pointed in a safe direction to avoid injury in case there’s a cook off. Always, keep your face away from the ejection port when clearing a hot chamber.
Don’t exceed the sustained rate of fire except under extreme circumstances, like if you are in a defensive position that is about to be overrun by a numerically superior force or assaulting through a near ambush. What isn’t considered extreme and should never happen is trying to expel remaining ammo when at the range.

Allowable sustained rates of fire are listed below.  
Weapon Rate of fire Max continuous rounds Time to expel rounds
M16 Series 12-15 rounds
per min
140 11.7 – 9.3 min
M4 Carbine 12-15 rounds
per min
150 12.5 – 10 min
M4A1 Carbine 12-15 rounds
per min
180 15 – 12 min

To learn more about indiscriminately firing rounds, check out the PS Magazine article Ammunition: Don’t Waste it!

Also, grab your CAC and check out the M4A1 Carbine / Reflex Fire Training article on the U.S. Army Combat Readiness Center website to see how things can go wrong. This one ended with a Soldier sustaining a fatal injury.
Leaders, make sure you know the weapon limitations and adhere to all cautions and warnings listed in TM 9-1005-319-10 (Aug 16, w/Ch 2, Apr 19) before running the next range.
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