What Is Boat Tail Ammunition
What Is Boat Tail Ammo?
To the uninitiated, the jargon used by members of the gun community can occasionally be confusing. Sometimes, people fly through different names of guns, parts and ammunition so fast it seems like an alien language. But before you download an app to learn Klingon in the hope of understanding people in the gun store, know you’re not alone.
Take, for example, boat-tail ammunition. What on God’s green earth does a boat have to do with ammunition? Is this some kind of prank where gun owners mess with people or is there really ammo being described this way? It isn’t a joke, and no one is trying to mess with you; there really is such a thing as boat-tail ammunition.
What Is a Boat Tail on Ammo?
The boat tail is the tail end of the projectile itself. It’s a reference to the shape of the rear end of the bullet. In boat tail ammunition, the end of the bullet seated within the brass has a shape that's somewhat tapered. In short, the shape actually resembles the rear of a boat, and that’s how it got the name. Interestingly, that shape does the same thing for the bullet as it does for the boat. One of the reasons you’ll see a boat tapered at the rear like that is to reduce drag.
What Is Drag?
Drag is friction that occurs in certain situations. One example is a boat flowing through the water. Another is a bullet flying through the air. Remember back in school when you would hear that for every action there is an equal and opposite reaction? That’s Newton’s third law, and it’s the principle at play here.
As the bullet flies through the air, it displaces that air. It pushes into the air, and the air has to go somewhere. The bullet fills the space where that air once was, causing a bit of a void to briefly exist where the bullet used to be. The air rushes into that area behind the bullet. In doing so, it pushes against the surface of the bullet, which slows the bullet's travel over time and can cause pressure on the rear of the bullet. That pressure can cause the bullet to fly differently.
To make a long story short, that opposing force can negatively impact how the round is flying. It can cause the bullet to lose power, rob it of the force it delivers into the target and make it less accurate. To mitigate these issues, the end of the bullet is tapered like a boat to allow for less friction in the rear.
Increasing Aerodynamics with Ammo Design
The point of a boat tail is to increase the aerodynamics of the round. Manufacturers work on the aerodynamics of the front of the round as well. The round will be traveling through the air at a high velocity. Drag is directly proportional to the velocity of the object traveling — meaning the faster something goes, the more drag there is. So, attention to the design of the overall round can increase aerodynamics and decrease drag.
Improving Ballistic Coefficient
This improvement in the ability of the bullet to fly is what’s called ballistic coefficient. The ballistic coefficient is the ability of an object to overcome air resistance while in flight, and it's a number that deals with velocity.
It’s a calculation using various aspects of the round like its mass, the area of the cross section encountering the resistance and the drag. The resulting answer to this calculation is the ballistic coefficient, and the boat tail design drastically improves this number. For example, let’s say you have two rounds of the same grain weight in the same caliber. If one is a boat tail and the other is flat, the boat tail ammo will have a higher ballistic coefficient number.
Why Isn’t Everything Boat Tail?
If a boat tail design is so good, why aren’t all rounds boat tails?
As the old saying goes, there’s more than one way to skin a cat, and this certainly holds true with bullet design. Boat tail designs are good, yes, but there are a variety of other ways of lessening the effects of drag on a bullet in flight. Ammunition manufacturers experiment with using different compositions, cores and powder loads, just to name a few.
Some rounds actually don’t bother with a boat tail because they’re using one of those other methods. Or, they’re relying on things like the velocity, rotation or weight of the round to deal with the drag. In some cases, manufacturers don’t bother with it at all because of the intended purpose of the round. Handgun rounds especially were designed for relatively short flights, so manufacturers are simply not as concerned with worrying about the drag on the round over time. It doesn’t matter as much because the rounds won’t be in the air that long.
Rifles and Boat Tail Ammo
As you’ve likely guessed by now, the main types of ammunition that use a boat tail design are rifle rounds. Given that the design is specifically meant to reduce drag and help rounds maintain energy over a longer flight path, it’s only natural that this design would go well with rifles. Rifles are often used to shoot over long distances, so any factor that can decrease performance, such as drag, must be addressed.
This is good information to help improve your shooting as well as when deciding to start handloading. Knowing how your bullet works can help you increase your accuracy, and knowing why things are made a certain way can help you choose your loading supplies. Maybe that’s why so many competitive shooters, especially at distances, load their own ammunition.
We hope this brief explanation has helped to illuminate why boat tail ammo matters so you can make more informed choices. We’re firm believers that all firearms knowledge increases your ability as a shooter. Maybe it will even inspire you to test out your own rounds to see which are boat tails and discover if they are working better than their flat counterparts. Either way — happy shooting!