What Is Hop-Up? A Basic Definition
So, you have been playing Airsoft for a while,[1] and you may have a favorite gun by now, which has become your go-to weapon. But there are probably some things that you don’t really like about the gun, too. Right? Amongst the things people wish for with their Airsoft guns, desire for a longer firing range is certainly at the top of the list. If this applies to you, then you are in luck, because there is something called “hop-up,” which can propel an Airsoft BB or pellet farther than it would otherwise have gone.
So, what exactly is this “hop-up,” you ask? Briefly stated: “Hop-up” occurs when backward spin is applied to an Airsoft projectile. This spin causes the projectile to experience “lift” due to the “Magnus Effect,” increasing the distance it travels.
Whoa! This a relatively complex definition. The remainder of this article will basically just be me attempting to break down these sentences into bits that are more understandable.
Breaking Down the Basic Definition
‘Backspin’
Let’s start with “backspin,” because you need the definition of that in order to understand everything else.
Backspin is a general concept and its definition applies to a lot of things – including balls (e.g., in sports) and cylinders (e.g., in physics and sailing) – that go beyond Airsoft. The simple definition goes something like this. “Backspin” designates a sort of reverse rotation (“spin”) exerted on a moving object (like a baseball or an Airsoft pellet).
That’s great. But how does backspin do anything for us in terms of effective firing range? Well, the right kind of spin produces “lift.”
‘Lift’
Here, “lift” refers to a physical force. It sort of acts against the force of gravity. Whereas gravity pulls an object – like an aircraft – down towards the earth, lift propels an object upward. It’s is one of the main reasons that an airplane is able to fly. An airplane wing is designed in such a way as to harness this lift force.
How does this impact the distance over which an Airsoft pellet can be fired? It all depends on something called the Magnus Effect, which I will explain now.
‘Magnus Effect’
At a Glance
It turns out that backspin, applied correctly, causes a moving ball to lift (similarly to an airplane wing). This result is termed the “Magnus Effect,” named after the 19th-century German scientist Heinrich Gustav Magnus.
The famed 17th-18th-century English physicist and polymath Sir Isaac Newton’s well-known Third Law of Motion states that for every action there is an equal and opposite reaction. So, when air applies a “push” on a projectile in one direction, there is a counteracting force acting on the object in the opposite direction.
In terms of Airsoft, then, when a pellet is fired the Magnus Effect can give it an extra distance boost. What happens is this. There is a layer of static air, called the “boundary layer.” According to Magnus’s explanation (as it applies to Airsoft), the backwards rotation of a BB pushes the air downwards and backwards, which gives the projectile an additional lift.
If you would like a longer, more complicated, and more in-depth explanation of the Magnus effect, I have one below. You can just skip it, as it is complex, but I would recommend giving it a glance, at least, because it is quite interesting (also I spent a really long time on this, trying to understand it).
In Greater Detail
“The Magnus Effect;” it even sounds complicated. And, in truth, it’s not overly simple. So this initial impression has some merit. But I am going to try to explain the concept as comprehensibly and understandably as possible – given that I am a grade schooler and not a physicist!
The Magnus Effect is a physical phenomenon. Gustav Magnus described the effect in 1852. It happens to things – like Airsoft BBs – as they move through “fluids” (including air) while spinning at the same time.
The path of a spinning pellet is different than the path of a pellet that is not spinning. In fancy terminology, this difference is called a “deflection” and it occurs because of the air pressing on the sides of the flying Airsoft projectile.
One of the most common examples of the Magnus effect is when a pitcher throws a curveball in baseball. The spin placed on the ball causes its path to deflect.
This deflection, whether in baseball or in Airsoft, can be explained by Newton’s previously mentioned third law. As the back-spinning ball or BB “pushes” down on the airflow, the air sort of pushes back, lifting the BB higher up (than it would have been without this spinning effect).[2]
Hop-up Devices
But anyway, back to hop-up. Hop-up-creating devices use the Magnus Effect to increase the range over which an Airsoft pellet can travel.
Theoretically, you could have at least two kinds of devices.
On the one hand, we can image placing a device on the end of a gun’s barrel. This piece might “stick out” or “protrude” from the barrel and apply backspin to a BB as it exits the barrel, right when it is just about to take flight.
On the other hand, the hop-up device could be part of the internal working of the Airsoft gun. In this case, they are built-in by the gun manufacturer and are usually installed between the inner barrel and the gearbox.
Adjustability
If you have an internally located hop-up device (as many guns have), you are first going to need to remove a small panel in order to adjust the hop-up on your gun. When present, this panel is usually located near the barrel of the gun. After the panel is removed, you should see either a dial, a slide, or a “drum dial,” which is basically a dial that turns differently from a normal one.
Adjusting hop-up is really easy. All you need to do is find your dial, slide, or drum dial, and move it a certain way. Typically, moving the slide away from the barrel increases hop-up, and turning the dial toward the barrel increases hop-up. Reduce hop-up by moving the slide or turning the dial the opposite.
However, before you do any of that, it is important to have at least a basic understanding of the various parts of the Airsoft gun. If you would like to read an in-depth article on the layout of an Airsoft, feel free to check out my article on the subject HERE.
For the most part, the barrel is really the only thing effected by the adjustment of hop-up. The length of the barrel also happens to be the main thing you should think about when it comes to BB-velocity management.
If you don’t know what that is, velocity management is the attempt to try to keep the speed of the BB (measured in “feet per second,” or FPS) as it is flying through the air the same as when it first leaves the barrel. Shorter barrels tend to allow the BB to have a higher FPS, at the cost of accuracy. But that’s a topic for another day!
Summary Thoughts on Hop-up & Hop-up Devices
However and wherever the hop-up device is placed, the point of it is to generate a spinning projectile. This spin, as we have seen, reduces the air pressure on the top side of the BB. In turn, this pressure differential causes the BB to travel farther and higher than it would have otherwise, thereby extending the effective range of the weapon.
But …and this is a key consideration …this range increase is accomplished without any increase in velocity. So, although the BB goes farther, the BB isn’t going any faster. From the point of view of kinetic energy, the “hopped-up” weapon is just as safe as it was before. It’s better living through physics!
Happy Airsofting!
Notes:
[1] Or maybe you haven’t been playing Airsoft that much, and I am simply abysmally incorrect! This is not a particularly uncommon occurrence.
[2] A fuller explanation will also invoke the concept of a “wake.” The process by which a wake will develop in a given airflow is complex. First of all, by “wake” I mean a “trail of agitated air created by the movement of the projectile.” At a certain time, the boundary layer of air “separates,” and it is at this point that the wake begins to develop. The boundary layer itself may or may not be turbulent (i.e., irregular in its flow), and whether it is or not, it will have a significant effect on the way that the wake is formed.