On the battlefield, there are few things as terrifying as a machine gun firing away.
What is even more terrifying is how big some of them can be. Two of the biggest machine
gun rounds still in common use around the world today are the .50 caliber BMG and the 20mm round.
These two rounds have been used for decades due to their immense power yet versatility
and ease of use in the number of weapon systems they can be employed against.
But how exactly do they compare? After all, they are both billed as long-range anti-personnel,
armor, and anti-pretty much anything you can think of. In deciding which one causes the most damage,
there are two main categories to consider. The first one includes its intended targets
such as personnel, tanks, aircraft, armored vehicles, and ships. The next
category is ballistics characteristics like velocity, flight path, and power.
Both the .50 caliber BMG round and 20mm cartridge for autocannons have a similar history.
John Browning designed the first .50 caliber machine gun during the First World War.
The US Army was inspired by French and German anti-tank and anti-aircraft rounds and wanted
something similar. While the machine gun to fire the .50 caliber round had its first prototype
by him around 1900, he redesigned it in 1917 to make the very first M2 machine gun, or Ma-Deuce,
as it is affectionately known by troops. The 20mm cartridge first came into existence
as the Oerlikon autocannon. The origins for the caliber actually came from Germany at
the end of the First World War for its use as an anti-aircraft weapon. But Germany lost the war and
as a result of the Treaty of Versailles was forced to give up most of their heavy weapons industry
including anti-aircraft weapons. Realizing the now futile venture, the inventors now found themselves
in and wanting to make a quick buck, they sold the rights to a Swiss company named Oerlikon.
Oerlikon developed the world’s first 20mm autocannon that was quickly adopted
by countries around the world. The US, Britain, Germany, Japan, Poland, Finland,
and others used either Oerlikon autocannons themselves or locally made derivatives of it.
Both the .50 cal and 20mm autocannon are devastating to personnel. Contrary to the popular
myth that these weapons are only designed for use against hard targets like bunkers and tanks,
these are both excellent anti-personnel weapons. While it might seem like overkill,
there are no rules explicitly banning their use against personnel in the law of armed conflict for
most nations. If you were unlucky enough to be on the receiving end of one of these rounds, there is
not much you can do about it even with body armor. The strongest body armor on the planet today is
known as Level IV armor. There are four levels of body armor with each level giving increased
protection. The highest protection level plates can stop up to a 30-06(pronounced thirty ought
six) round which produces about 2,500-foot pounds of energy. Compare that to the average of
15,000-foot-pounds produced by the .50 cal and the 38,000-foot-pounds made by the 20mm round and it
is easy to see why no one hit by either of these powerful cartridges stands a chance of survival.
How the weapons perform against tanks is a different story. There are many types of .50
caliber ammunition types and the most powerful one of those is the .50 caliber Saboted Light
Armor Penetrator. The SLAP round was designed in the 1980s by the US Army and Marine Corps to
punch through the armor of armored personnel carriers and light tanks.
It works by using sabot technology of pushing a small, steel rod through the armor that allows
the energy of the bullet to pass through it. These rounds are capable of penetrating up to
19mm of armor out to a 1500 meter range. Such capability is impressive for light
armored vehicles and mounted machine guns but not so much for tanks. The most capable Main
Battle Tank in the world today is undoubtedly the US M1A1 Abrams. This tank’s advanced armor
offers up to 700mm of protection for standard high explosive rounds and up to 350mm of protection for
sabot-type ammunition. Even other less capable tanks like the T-72 offer 450mm of protection
and about half of that for sabot rounds. The 20mm autocannon fares equally as bad against
tanks and performs worse against lightly armored vehicles. The 20mm round can penetrate up to 6.3mm
of armor at the same 1500 meter range as the .50 caliber SLAP rounds. They perform better at
shorter distances with up to 12.5mm of penetration out to 500 meters before it starts declining.
For a reference point, some of the most common armored vehicles around the world include the
BTR-70 and BMP, both Soviet-designed vehicles that inspired many locally produced versions,
each has 7mm and 23mm of armor respectively. A ZSU anti-aircraft gun, again a commonly used and
exported Soviet design used for anti-aircraft and anti-armor purposes, has 9mm of armor.
Now, the US Navy does use a similar sabot technology in its Close-In Weapon System that
fires 20mm rounds as a last resort against missile threats but this makes up only a limited amount of
the ammunition. Why the .50 caliber round performs better against armored targets than the 20mm round
is simple physics. Though the 20mm produces more foot-pounds of energy, this energy is dispersed
over a wider surface area. The .50 caliber SLAP rounds produce less overall energy but have a
much smaller surface area making this energy more concentrated that punches through armor easier.
Now, of course, the .50 cal SLAP rounds are not as common as the .50 cal BMG ammunition, but
this comparison includes all types of ammunition that can be shot from one of these weapon systems
since they are all the same caliber. Besides armor, both rounds perform
equally well against aircraft. After all, that is what they were designed to do. Aircraft,
as a general rule, do not have as much armor as ground targets do since their
main defense against ground fire is their speed and maneuverability. Adding extra armor increases
the weight and cuts down these critical factors actually making it more dangerous for the pilots.
For use against ships, the advantage has to go to the 20mm round. When one says ships that does not
mean you could take down a battleship or even a modern destroyer. Rather, use against small
surface contacts like powerboats and speedboats such as what pirates and terrorists use is what
the intended targets would be. The 20mm round wins here because of its range. The max effective range
of a .50 caliber BMG is about 2000 meters. The 20mm round is almost double that. In a maritime
environment, distance is your friend since it gives you more time to assess the situation
and more opportunity to strike the enemy. Though both weapon systems are employed by naval forces
around the world, including the US Navy, the 20mm round is the go-to for these kinds of targets.
As far as the kind of damage the .50 caliber round and 20mm round can inflict,
they are equally devastating rounds. Against personnel targets, they both slice through
with ease. The edge for armored vehicles has to go to the .50 caliber round only because one
of the variants specifically designed for it can punch through most armored vehicles in the world.
The 20mm still packs a wallop in this case but just not enough to beat the SLAP rounds.
Against hardened targets like tanks, they both lose out just because tank armor has
advanced so much over the past fifty years that a man-portable anti-tank rifle round
is not truly feasible anymore. They both perform well against aircraft, and against small surface
vessels the 20mm round wins due to its ability to deliver effective energy over a longer distance.