Burst Fire Misconceptions

Burst Fire Misconceptions

Ever been issued a rifle or SMG that had a 3-round burst? You were probably told it was there to keep you from spraying and praying.


Three-round burst was created to disburse bullets, not to improve accuracy or controllability. Nor was it, contrary to popular belief, created to conserve ammunition. Quite the opposite, in fact.

But before I explain how and why, let’s agree on the meaning of some relevant terms.

Semi-automatic means self-loading. After you fire, the gun sticks another live round in the chamber, but waits for you to move the trigger to fire again.

Fully automatic means that the gun keeps shooting till you let go of the trigger or run out of ammo, whichever comes first. 

Sometimes, people use the term “auto” or “automatic” when they really mean semi-auto only. In common usage, “.45 auto” refers to the semi-automatic Government Model and its clones. That GI .45 goes “Bang! Bang!” rather than “Rat-tat-tat!” In this narrative, auto or automatic will mean capable of more than one bang per trigger press.

With submachine guns, which shoot pistol bullets, automatic fire can be useful to turn that glorified pistol into a shotgun, with several bullets hitting the subject in rapid succession.


Automatic Options

If you have been conditioned by your TV or video games to believe that bad guys fall down and remain motionless after only one hit, you may think a burst of automatic fire to the chest is overkill. The last REAL bad guy I saw face down in his own blood took 8 or 9 hits from full power, law enforcement 9mm and .40 caliber hollow points before he stopped pulling the trigger of the AR he’d stolen from a cop and used to murder other cops.

Two of the three law enforcers hit by rifle bullets in that gun battle were DRT–dead right there. All three were hors de combat (out of action) with only 1 or 2 hits from rifle bullets.

That means that automatic fire is less necessary with rifles than SMGs. When you do need full auto, it’s likely to be at close range. The Border Patrol and Department of Homeland Security qualification courses we shot only called for automatic rifle fire inside of 7 meters or so.

At longer ranges, automatic fire is rarely useful in military combat, unless fired from a belt-fed machine gun. I trained force on force every afternoon, 5 – 6 months a year, for 3 years in a row, with MILES, the military’s Multiple Integrated Laser Engagement System. I got pretty good at small unit tactics. In that whole time, I selected automatic TWICE.

When you do use automatic fire, short bursts tend to be more efficient than spray ‘n’ pray (refer to Agent Garcia’s demonstration in The Evolution of Police Long Guns). Short bursts of 2 – 5 rounds waste less ammo and hit intended targets more. People think that’s why “burst” selectors, mechanical devices limiting automatic fire (usually to a maximum of three rounds), came about.

Not so.

The burst fire concept was intended to reduce training time for uneducated conscripts by spreading bullets around like a shotgun. The theory was, it takes time and treasure to train a recruit in the fundamentals of marksmanship required to hit a man sized target at common combat distances (roughly 0 – 350 meters). Proposed hardware solutions to this software problem included multiple projectile cartridges that would spew out 3 bullets per shot. When designing and manufacturing cartridges to do that proved to be unworkable, designers moved to rifle receivers, implanting extra parts that, when selected, cause the gun to fire 3 rounds per trigger pull.

The theory behind each of these stratagems was, a raw recruit will probably miss, say, off to one side of where he or she is aiming. If there is one bullet flying left of where s/he aimed, and one to the right, one of the three bullets will connect with the target.

This might be well and good on a foreign battlefield where “collateral damage” is undesirable but acceptable. It’s next to useless in Stateside law enforcement, where “suppressive fire” is rarely acceptable.

Burst limiting mechanisms are NOT effective for controlling muzzle climb in automatic fire. There are various mechanical and body indexed means of limiting the tendency of the barrel to tilt up for the first few rounds. But even if you don’t use them–say you have no muzzle brake, and your hold is relaxed, during a long string of automatic fire–the muzzle will only climb for the first three rounds or so. After that the gun “settles in” and merely rocks back and forth, unless the cartridge is so powerful it probably should not be fired on fully automatic out of an individual weapon.

What does all that verbosity mean? In short, 3-round burst stops firing at the peak of muzzle climb, before it has a chance to settle in. Then the gun stops firing and drops down below where it would have “settled” during a longer string of automatic fire. Then you have to start all over again with another burst. Burst fire makes for more up and down movement of the muzzle, not less

Up close, where automatic fire may be useful, any moderately trained individual can fire short bursts of automatic fire from a fully automatic, intermediate cartridge rifle or SMG.

Here’s the secret: If you want it to stop making noise, simply remove your finger from the trigger. That’s some Zen-level understanding there. But remember, it’s a secret. Shhhh . . . Don’t tell!

When I was in Law Enforcement Submachine Gun Instructor training, one of our trainers was former Royal Marine Clive Shepherd. Clive used to say he could play a tune on a submachine gun by controlling his trigger finger.

H&K made various selector options for their MP5s. The first US rifle issued on large scale with a 3-round burst selector was the M-16A2, which came about in the mid 1980s.

A2 on an A1

In the early 1990s, I got off active duty (I’d been a rifleman issued an M-16, not even an M-16A1) and joined the Wyoming National Guard. The Guard hosted rifle “clinics” at Camp Guernsey. At one or two of those clinics I was coached by Bev Spungen, the first female all-Army rifle champ. The “hot ticket” for service rifle competition in those days was an M-16A2 upper receiver on an M-16A1 lower receiver.

The A2 upper had a heavier barrel, a higher rate of twist, and a crisper set of iron sights more easily adjustable for windage and (especially) elevation. Ironically, Eugene Stoner had made his original AR-15 design with easily adjustable sights, but the Army generals thought the average GI was too stupid to be trusted with sights that can be rapidly changed by hand. They insisted on the complicated “tip of a bullet” adjustment for the M-16s (and later M-16A1s).

The A1 lower, which did not have the A2’s ridiculous burst cam, had a much more consistent and workable trigger. Hence, the A2 on an A1 . . . if one had a connection in the unit armory who could pull that off for the competitor.

Bye-Bye Burst Cam . . .

When I first joined the Border Patrol a few years later, our station had a few surplus Army M-16A1s, and even some M-14s. About March of 1997, my BP station converted to factory new M-4A1s. Border Patrol said they’d buy M-4s direct from the manufacturer, but Colt had to yank out that stupid ratcheting burst cam first; hence the M-4A1. Unlike the M-4 and the M-16A2, the M-4A1 had full auto capability.

The burst cam created to give the M-16A2 (and later, the M-4) a 3-round burst capability actually changed your semi-automatic trigger pull between shots. It was also that many more moving parts to break. Dumb.

. . . About the Time US Customs was Demanding One

In the bad old days, legacy US Customs had patrol officers. It still has one patrol unit left: the Shadow Wolves. An exclusively Native American outfit, they cashed in their ancestors’ ponies for 4 wheelers, and track smugglers in the vast desert of SW Arizona. The legendary Brian Nez of the Shadow Wolves taught me M-4 during my most recent Firearms Instructor Recert course.

Most people state and local police officers encounter throughout their workday are not bad guys. Cops interact with the public, only some of whom are bad guys. Like most federal investigative agencies, Customs dealt almost exclusively with bad guys. Federal special agents investigate suspected bad guys, confirm they are in fact bad guys, and if so, serve search and arrest warrants on bad guys. On surveillance, smaller guns under plain clothes are the norm (although we had long guns in our trunks, just in case). But when it’s time for the take down (or, if it’s a large criminal organization, “roundup”), long guns are the rule, not the exception.

Legacy US Customs was influenced, to a greater extent than most people would believe, by the 1980s television show Miami Vice. “Sonny Crockett” carried a Steyr AUG rifle during takedowns, so by golly, Customs wanted one too. No, I’m not making that up.

The AUG was an outstanding bullpup rifle, firing the 5.56x45mm intermediate cartridge. Then US Customs lawyers / CYA administrators got in the mix. They demanded that Steyr convert its auto function to 3-round burst (sound familiar?), and that the trigger pull be increased to something outrageous like 14 pounds.

Both changes were lawyers’ solutions to problems that do not exist.

The Steyr engineers must’ve thought Customs was a bunch of idiots–till they realized that they were well-funded idiots, who would buy a large number of AUGs if the changes were made. It must’ve pained Steyr’s engineers to take their beautiful, thoughtfully designed bullpup and essentially downgrade it to stack the odds in favor of the bad guys–but it didn’t bother them enough to lose such a large contract by standing on principle.

The AUG burst mechanism always reset to zero, so every trigger pull on burst got you 3 rounds (till you ran out of ammo). In that, it was an improvement over the M-16A2 burst cam, the first burst of which could be 1, 2, or 3 rounds. The AUG burst feature did require the inclusion of what we called a “screen door spring,” one of the few AUG internals likely to break.

The AUG survived the Customs – INS – Border Patrol Anti-Smuggling Unit merger of 01 Mar 2003, which eventually formed Homeland Security Investigations. AUG parts were getting harder to come by, though, partially due to import regulations. It was ironic, but a splendid example of the rule of law, that import regulations should hamper the primary enforcement agency of import regs. Within a few years, HSI traded in the old AUGs for M-4s.

Not M-4A1s.

Yes, the burst was back. Why? I’ll give you a hint: the people running ICE were almost never gun toters.

Except for one former FBI agent during the Obama administration, the Chief of the Border Patrol had always been a Border Patrol Agent. That meant major procurement decisions go through a chief executive who has actually used that type of equipment, for the purposes it was designed to accomplish, in the field, in the chaotic, stressful conditions of law enforcement.

Conversely, the head of ICE, of which HSI is a part, is almost invariably a former Assistant US Attorney. AUSAs prosecute federal cases, but only rarely have ever enforced the law in the field (if they had, it was during a different career, before they went to law school).

The M-4s, even with their ridiculous burst cam, did have some advantages over the AUG.

The M4 series not only gave DHS commonality of easily acquired parts, they also made training easier. Many agents were former active duty military, and / or current reservists, who had already trained on Armalite series rifles (ARs) such as the M-16 and M-4.

The flat top Picatinny rail of the M-4 allows for a mix of different sighting systems, depending on need, and upgrading sighting systems as new optic technologies become available. The Customs AUGs had in integral 1.5 power scope with a thick dark circular “doughnut of death” reticle. Made by Swarovski Optic, it gathered light well in twilight, but was nearly useless in the dark.

Unlike the venerable AUG, it looks like selectors limiting cops and soldiers to burst fire are here to stay. Fortunately, most of the weapons with selector switches tend to use rifle cartridges, which makes fully automatic less necessary.

If you want more definitive information on the evolution of the burst fire concept in general, and the development of the Armalites from AR-15 to M-16A2 in particular, I highly recommend reading Edward Clinton Ezell’s Great Rifle Controversy.

–George H, lead instructor, Heloderm LLC

Update: M-4 to M-4A1

I recently read on the internet (which never gets anything wrong, of course) that until the next generation “M-5” infantry rifles are developed, procured, and fielded, the US Army is in the process of converting the M-4s (with the stupid burst cam) into M-4A1s (capable of full-auto). As with the adjustable sights of the M-16A2, they are once again re-inventing the wheel.

Short bursts are a good idea when storming a position. Mechanical contraptions that limit automatic fire to burst only were stupid from the start. It took them 4 decades too long, but I’m glad the Army finally clued in on that.