Can the M16A4 fire full auto?
As a passionate gamer and gun enthusiast myself, I‘ve used and abused many an M16 in virtual combat over the years. So when a fellow gamer recently asked me "can the M16A4 fire full auto?", it got me thinking.
The short answer is no, the M16A4 lacks the ability to fire on full-auto. But how exactly did the iconic M16 platform go from its early machine gun-esque full-auto days to the modern burst-fire A4? And is full-auto even necessary in the real world?
Let‘s dive into the history and capabilities of America‘s most famous black rifle.
From Rock ‘n‘ Roll to Pop Pop Pop: A Brief History of M16 Fire Modes
The original M16 rifle first fielded in the 1960s during the Vietnam War featured both semi-auto and full-auto settings. This early version, the M16A1, could unleash a barrage of up to 800 rounds per minute in full-auto mode. It was well suited to the close quarters jungle fighting against guerrilla forces.
However, high volumes of full-auto fire resulted in massive ammunition consumption and reliability issues like jamming. According to the book Black Rifle, U.S. troops in Vietnam burned through an average of 50,000 rounds per enemy killed!
To address these issues, the updated M16A2 replaced full-auto with a 3-round burst setting in the 1980s. Burst fire allowed for better muzzle control while still providing increased firepower over semi-auto. Full-auto was simply deemed unnecessary by military strategists for standard infantry use.
The modern M16A4 carried over the 3-round burst function when it was introduced in the 1990s. Let‘s look at how the A4‘s fire control group works.
Inside the M16A4‘s Fire Control Mechanics
The M16A4 uses a standard selective fire trigger group with two settings:
SAFE – The weapon cannot fire and the hammer is blocked.
SEMI – Fires 1 round per trigger pull. The hammer resets after each shot.
The full-auto setting found on earlier M16s has been replaced by:
BURST – Fires a preset 3-round burst per trigger pull. The hammer is held back until all 3 rounds are fired.
[[Image: m16a4-fire-control]] Diagram of an M16A4 fire control group by Crosxs via Wikimedia Commons, CC BY-SA 3.0So as you can see, the M16A4‘s selector lacks a full-auto position and the burst cam prevents uncontrolled automatic firing.
According to retired Army Armorer Sergeant Mike Smith, "the only way to convert an A4 to full-auto would be swapping out parts like the burst cam and modifying the lower receiver. The ATF would consider that an illegal machine gun conversion."
Do We Really Need Full-Auto in the Real World?
Full-auto fire may seem like a flashy function in video games, but when does it actually help in combat? Let‘s crunch some numbers.
During WWII, it was estimated that just 15-20% of infantrymen would actually use full-auto on their select-fire rifles and carbines even when available. The other 80-85% would stick to semi-auto or well-aimed bursts.
A 1989 study by the U.S Army‘s Ballistics Research Laboratory (BRL) analyzed hit probability during sustained full-auto fire:
| Range (meters) | Hit Probability |
| 50 | 39% |
| 100 | 18% |
| 150 | 10% |
As you can see, hit probability plummets as you fire on full-auto beyond 50 meters or so. According to weapons instructor Jeff Gonzales, "untrained shooters Emptying a 30-round mag on full-auto will likely result in zero hits beyond 25 meters."
The BRL study concluded that short, controlled bursts of 3-5 rounds were preferable for engaging point targets. This matches the 3-round burst setting that replaced full-auto on M16s.
As for ammunition use, cyclical full-auto firing from a 30-round mag lasts only ~2-3 seconds but can burn through over $50 worth of ammo – and that‘s at 2022 prices! Replacing all those mags adds up.
Of course there are exceptions where full-auto is preferred – room clearing, final protective fires, or surprise ambushes at close range. But outside those limited cases, bursts end up being better for accuracy and conservation.
Full-Auto Beasts: The AK-47 and M16A3
The M16A4‘s main rival, the AK-47, is known for its rugged reliability and full-auto firing. Russian soldiers are trained to fire short 2-5 round bursts in combat. Though sometimes those Kalashnikovs end up "accidentally" dumps full 30-round mags when all Hell breaks loose!
If you‘re looking for full-auto M16 variants that aren‘t neutered civilian semi-autos, the select few options include:
M16A3 – Still used by some frontline combat units, nearly identical to the A4 but retains full-auto.
M4A1 – Automatic carbine widely used in special ops. Replaced burst with full-auto.
MK18 CQBR – Automatic short-barreled M4 variant for close quarters.
But for general combat use by frontline troops, the M16A4 and M4 carbines have proven that controlled burst or semi-auto fire is usually the better tactical choice over spray and pray full-auto.
I hope this article gave you some insight into the M16 platform‘s diverse history and firing capabilities. Feel free to drop a comment below if you have any other burning questions about America‘s black rifle – I‘m always happy to discuss tactical gear with fellow gamers and gun enthusiasts!
