A lot of people wonder how fast a bullet travels and what affects that speed. For this article, we are going to stay with hand and shoulder-fired weapons.
If the gun needs to be mounted on a tank, airplane or battleship, then we will not discuss those.
The three major things that affect bullet speed are powder charge, barrel length and bullet weight. We look at these three points and explain what they have to do with bullet speed. We also tell you the slowest commercially made bullet and the fastest made.
Factors Affecting Bullet Travel
1. Speed
Bullet speed is measured in Feet Per Second (FPS). Ammo makers list an FPS on the boxes of ammo they sell.
Just like a car and the gas mileage, the actual speed of the bullet will vary. Even if you shoot a batch of ammo in the same gun, the bullet speed can vary as much as 100 FPS.
Weather conditions can also affect bullet speed.
Bullet speed is also measured within a few feet of the muzzle. As the bullet continues on its flight path, it slows down.
2. Powder
Powder is the first part of determining how fast a bullet will move. Powder is measured in grains. 1 grain is equal to 0.00228571 ounces or 0.0647989 grams.
People who reload their ammo know they can change the speed of a bullet by changing the powder type and powder load, also called the charge. Just dropping a charge by 5 grains may make a bullet move several hundred feet per second slower.
Gunpowder has come a long way since the first crude black powder was made by the Chinese. Today, powder makers produce hundreds of varieties of powder.
3. Burn rate
Each powder has a set burn rate. While burn rate is measured in tiny fractions of a second, it does matter. The powder burn rate is a big part of figuring out the pressure inside the barrel when the gun goes off.
Powder makers typically do not list the burn rate on powder containers. Rather, they list the calibers the powder is suited for.
Warning: Loading pistol powders into rifle cartridges can lead to dangerously high-pressure levels. YouTuber Scott DeShields had a .50 BMG blow up and the shrapnel from the gun came close to killing him.
Gun maker Mark Serbu believes the ammo was loaded with pistol powder by someone other than Scott.
4. Temps
Temperature will also affect how a powder performs. Most powders perform best around room temperature. Too hot or too cold and the powder does not burn as expected.
Some shooters in Arctic conditions will keep ammo next to their bodies to keep them warm. They load when they need to shoot.
Black Powder warning: Also, you should never use modern powder in a black power gun. Black powder has a really slow burn rate. Black powder guns are not built to handle the chamber pressures of modern powders. The gun will explode with modern powder.
YouTube has plenty of videos showing professional shooters exploding blackpowder guns while they hide behind a barrier.
5. Barrel
Barrel length has a lot to do with bullet speed. Short barrels give less speed than long barrels. In a short barrel, the powder has less time to fully burn. The expanding gasses do not have time to reach maximum size.
Longer barrels let more powder burn and burn more fully. This means a bigger gas cloud to push the bullet from the barrel.
This idea is studied by gun and ammo makers and gun enthusiasts. Barrel length varies by gun. Bullet speed will vary by cartridge and gun, so there is no one-size-fits-all formula.
You can get too much barrel and the bullet will slow down in the barrel. This is usually not a problem as barrels that long are for specialty use.
6. Squib
An exception, no matter how long the barrel is, is something called a squib. A squib load means the cartridge did not have enough powder to push the bullet out the end of the barrel. The cartridge may not have any powder at all and the primer delivers enough force to push the bullet partly down the barrel.
Experienced shooters can tell if they have a squib. They stop shooting and clear the bullet. Continuing to fire a gun with a bullet stuck in the barrel is both dangerous to the shooter and could damage the gun.
7. Weight
Bullet weight matters. The .30-06 is a great example. This venerable cartridge will take bullets from 110 grains (I am not including sabots) to up to 250 grains.
The same powder charge will push the bullets at vastly different speeds. The 110-grain pill is the fastest-moving bullet for the ’06. The 250-grain is the slowest.
The US Military studied the ’06 and velocities. Their chart shows the 110-grain moves along at 3,505 FPS. Conversely, the 250 grain seems to trudge along at 2,476 FPS. Neither of these are particularly fast and they are far, far from being slow.
This is just a matter of physics. It takes more force to move something, the heavier it is.
What is the Slowest Bullet?
So, what is the slowest bullet? Even if we include spring-powered BB guns, the slowest bullet is fired from a real gun using a chemical reaction. The primer going off and the powder burning are both chemical reactions.
There is no clear winner on the slowest bullet. Different guns, different loads and barrel lengths all figure into this. If you include bang sticks in the gun category, then bullet velocity may be a couple hundred FPS. Bang sticks have little to no barrel.
What matters is that everything works together to push the bullet out of the barrel. All commercially made ammo will do this when using a gun in good condition.
You could hand load a cartridge so the bullet’s muzzle velocity would be less than 100 FPS. Unless you are very experienced with guns and know how to clear a squib, do not do this.
Contenders for the Slowest Bullet
A few contenders for the slowest commercially made bullets fired from short-barrelled pistols are are:
1. 6mm Flobert
This is an old rimfire round that only has a primer compound, no powder. It runs around 250 FPS.
2. .22 CB cap
This is a short 22 caliber brass with only the primer compound to fire the bullet. It runs as low as 350 FPS.
3. Daisy Red Ryder
This spring-powered BB gun shoots the BB out at around 350 FPS. (Technically not a handgun, but someone will ask for the FPS.)
4. 2mm Kolibri
A 3-grain bullet at 660 FPS. This also uses just the priming compound to fire a bullet.
What is the Fastest Bullet?
Where the fastest bullets are concerned, we have a lot more data and we have three qualifiers for the winner’s podium. We also have an upper limit thanks to testing and plenty of research.
The maximum velocity of a shoulder-fired bullet with today’s technology is around 5,000 FPS. That is a screamer compared to other ammo on the market today.
Lots of gunsmiths have tried to push past that envelope, but no one has succeeded.
The .223 or NATO 5.56 is often called a “high velocity” round. It is not. The standard for a 55-grain full metal jacket (FMJ) pill is around 3,200 FPS. This is the upper end of the medium-speed rounds.
Contenders for the Fasted Bullet
Here are the top 3 fastest commercially made rounds and 2 wildcats.
1. .220 Swift
The .220 Swift fires a .224 diameter, 40-grain bullet as fast as 4,600 FPS. That is the hottest load. More typical speeds are 4,200 FPS with the 40-grain and around 3,600 with the 60-grain projectile. The .220 Swift was designed as a varmint gun, particularly for prairie dogs. It is very accurate.
2. .204 Ruger
The .204 Ruger is a newcomer, created in 2004. A .204 diameter, 32 grain proj with factory loads has an estimated 4,225 FPS. This, too is a screamer and holds its own against the .220 Swift. It is a varmint gun.
3. .22-250
This round started out as a wildcat, but soon gained the attention of varmint hunters and folks who wanted more punch with less recoil. It spits a 40-grain projectile at 4,200 FPS.
The .204 is slightly faster, but not by much.
Also Ran
Two cartridges bear mention here despite never being available except as a 1-off from the maker.
22 Eargesplitten Loudenboomer
The Eargesplitten Loudenboomer is a definite bit of wordplay by P.O Ackley, a gun designer who created this one in the 1960s. Ackley took a .378 Weatherby Magnum case and necked it down to a .22.
The result pushed a 55-grain bullet to a maximum of around 4,600 FPS, just the same as the .220 Swift.
The .22 Eargesplitten Loudenboomer is not a commercial cartridge. It is a wildcat round in gun terms. Ackley made it as a test project.
Unnamed
If Roy Weatherby named his .378 brass necked down to .30 caliber, I can’t find a name for it. Regardless, the cartridge pushed a bullet (or fragments in some cases) nearly 5,000 FPS.
THE PROBLEM
All the fast bullets have the same problem: barrel wear. Simply put, these screamers destroy barrels.
Barrel burn, as it is called, is when the burning gasses destroy the rifling in the first few inches, the breech, of a barrel. This is erosion, not melting.
The metal in the breech also swells (hot) and shrinks (cools down). This also creates microscopic cracks in the metal, which is not dangerous. More shooting means the gasses get into the cracks and create more heating, cooling and wider cracks.
Put another way, shooting a powder-propelled cartridge is like putting a torch to metal. Sooner or later, the metal will show wear.
The hotter the torch, the more and faster the wear appears.
Conclusion
How fast a bullet travels is due to a lot of different things. The powder charge, the bullet weight, barrel length and even shooting conditions all matter
Shooting a bullet in an atmosphere, like on Earth, means friction with the air will slow the bullet down and eventually make it stop. Gravity will also slow it down, or speed it up. In the case of speed up, the bullet eventually reaches a terminal velocity and it cannot go any faster.
More important than bullet speed is the performance. The 2 main performance indicators you want from a bullet are:
- Accuracy
- Foot pounds of energy on impact.
A super fast bullet that groups 10 inches at 25 yards is useless, except as a bad example. A low bullet that puts every shot in the same hole at 25 yards is superb.
Foot pounds is how much terminal force the bullet delivers on impact. You want enough to get the job done. And that, gentle reader, is a topic for another column!
