The terms ‘HOP-up’ or ‘HOP-up bucking’ are mentioned regularly in airsoft and as a player, it’s important to know what one is and how it functions. We’ve put together this handy hop-up bucking guide so you can find out everything you need to know. You’ll learn how to choose the best HOP-up unit, so you can tune your AEG perfectly and get the best bang for your buck.
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The HOP-up, or ‘HOP’, inside your AEG, Sniper rifle or GBB provides backspin to the BB as it enters the inner barrel, allowing the BB to travel further and with greater consistency. There are two main types of hop-ups available, either AEG type or GBB/VSR type.
When a BB is loaded, it comes in contact with the HOP-up bucking which causes friction on one side of the BB. This provides backspin to the BB, allowing it to travel beyond the point that a gun without a HOP would reach. As a result, the gun achieves a greater range, while still maintaining non-lethal power levels.
Put simply, the Magnus Effect is the observable behaviour of a spinning object as it travels through Air, which cannot be observed when the same object is not spinning. This relates to differentials in Air pressure caused by the spin, similar in principle to the Aerofoil effect observed in the wings and control surfaces of an Aircraft. But enough with the Physics lesson, as it relates to Airsoft the Magnus effect can be observed in BBs provided with backspin through contact with a surface which causes friction on one side of the BB (the HOP bucking), extending the range and providing an upwards force allowing the BB to travel beyond the point that gravity alone would have it fall.
In principle, all adjustable AEG HOP units work in a very similar manner and many share common buckings and nubs. Obviously, if you are fresh to the sport of Airsoft, this doesn't make anything less complicated, so here in this blog we will outline the components of a HOP unit, get you up to date on terminology, and the pros and cons of using particular HOP-units over others. Compatibility-wise, there are two main types of hop rubber/bucking available, either AEG type or GBB/VSR type, and whilst they differ in appearance they provide the same function for each platform. Having such a wide range to choose from may sound daunting if you’re new to Airsoft, so we’ve included all the terminology you’ll need to know in this hop-up guide.
The bucking is the rubber piece that makes direct contact with the BB during firing, providing backspin and extending the range of your shot. These are usually in the form of a small rubber tube of varying hardness that goes over the chamber end of your inner barrel, interfacing with grooves cut in the chamber end of the outer surface of the barrel. The hop bucking you choose will largely depend on what FPS your replica shoots, or your target FPS for your build. The harder the bucking, the more effectively it will apply hop to higher FPS replicas. The reverse of this is also true, as a harder material will decrease the effect of the HOP-up on lower FPS builds.
The nub is the component that pushes on the Bucking when it itself has pressure applied to it by the arm and adjuster. This is usually in the form of a tiny plastic or rubber cylinder but can is also offered with a flat surface on one side, or with a groove down the center in more specialized nubs. This part allows the amount of contact the bucking has with the BB to be varied as the nub pushes through the "HOP window", a usually square hole machined into the chamber end of the inner barrel. Variations of HOP nub and their uses can be found below:
The H-Nub is one of the more common HOP enhancements available. This type of nub is cylindrical but with an hour-glass shape or "H" profile, and aims to provide more stable HOP application by applying pressure evenly to both sides of the BB. These are suitable for any AEG and can be easily installed, with effective results.
The Flat Hop Nub is a nub with a rounded side, to interface with the adjuster, and a flat side to put pressure on the BB. The theory behind the flat nub is that its larger contact surface will provide greater pressure and allow a greater level of hop to be applied. Flat hop nubs are designed for high FPS builds and DMRs which use heavier BBs by default, but can require a lot of fine-tuning to set up well.
R Hop refers to a small patch of rubber that can be installed over the inner barrel window before the bucking is installed and effectively increases the HOP effect by adding further pressure to the BB. These patches usually need attachment with glue and are prone to failure, but provide a significant increase in range and accuracy when done right.
The Adjuster is the part you will physically turn or move, to increase or reduce the amount of HOP up force applied to your BB. This can be found in several forms. The more common types found on AEGs are the Gear, Rotary, and Slider. These are generally found either in or near to the chamber area of your Airsoft AEG and are sometimes concealed behind a small door or the mock bolt carrier should your AEG have one. The most common types of adjusters are listed below:
Gear Adjuster - The most common type of adjuster for M4/AR15 platform AEGs. Gear adjusters are easy to adjust quickly but are not as easy to adjust in fine increments. The gear adjuster is one of Tokyo Marui's earliest designs, and as such it has a plethora of replacement enhanced units available and has proven itself reliable over its nearly 3 decades of use. Gear adjusters can also be found in some HK33 and SMG5 replicas. Gear adjusters are also prevalent in GBB pistol replicas, primarily due to the space confines within the internals of a pistol.
Slider Adjuster - The most common type of adjuster found on AK47/74 replicas. Slider adjusters are not as quick to adjust from zero to full HOP as the gear but provide a greater ability to adjust the unit in small increments. These have been on the market since Tokyo Marui released its AK47, AK47 Beta Spetsnaz, and AK47S in the late s. Slider adjusters are also used on older designs of SMG5 replicas.
Rotary Adjuster - The rotary HOP unit was first used on the Tokyo Marui AUG AEG and has since found its way into the majority of AR36, P90, AUG, and G3 AEGs. The Rotary HOP adjuster allows a great middle-ground between quick adjustment and accurate fine adjustment and applies pressure on the nub directly from above. This minimizes the possibility of applying uneven pressure to the nub which is a common cause of inaccuracy at long range. The Rotary unit is widely regarded as the best design for these reasons, and more recently designed M4/AR15 AEGs now features a Rotary type adjuster.
TDC Adjuster - TDC stands for top dead center, meaning the adjuster is positioned directly above the point of contact where the nub meets the rubber. This is most commonly found on sniper rifles and can be added as an aftermarket option to those which don't include a TDC out of the box. TDC adjusters began their life as a homebrew option for accurizing sniper rifles and NBB pistols, and provide the absolute most precise adjustment for your HOP. This comes at a price, however, as TDCs adjust via a grub screw and as such they will need a very small Allen key to adjust, reducing their ability to adjust during an engagement in the field.
The HOP up Arm is the piece that transfers the pressure from the adjuster to the nub. These are available as reinforced parts, and whilst there is no harm in upgrading this piece as a preventative measure, reinforced HOP Arms would generally be more useful in high-FPS builds which will cause more wear and tear on the Arm by their nature, especially when used with a considerable amount of HOP applied.
The HOP chamber/unit refers to the piece which receives the BB when the magazine is inserted and houses the HOP parts which apply the backspin to your BB. When shopping, this term is often used to refer to a complete unit and also a bare-bones unit for which you will have to use the small parts from the unit you are replacing. These are available in polymer, Alloy and CNC machined aluminium for various AEG and Sniper rifle platforms. The material you choose doesn't really matter, as the most important thing a hop unit can provide is a tight fit and good air seal. There are advantages to using a metal hop unit, for example, they are less prone to breaking, especially if you use a metal nozzle or a high rate of fire setup, and CNC units provide an immaculate fit which can only really be achieved with precision-engineered parts. For the most part, polymer units function perfectly fine and are often the only part of the HOP set up which I personally don't recommend changing, other than in the case of high rate of fire builds.
The hardness of a HOP rubber is a metric for how much backspin the HOP unit will apply to BBs traveling at a certain velocity. Most out-of-the-box AEGs of UK power levels should be using a rubber of hardness between 50 and 60 degrees. Generally, the softer the rubber the more HOP is applied, though this comes at the cost of the softer rubbers wearing out more quickly and often providing too much backspin when used at higher velocity levels. Higher velocity setups may require harder HOP rubbers, as the impact of the BB hitting the hop rubber will be much heavier and may cause tears in softer rubbers. As the Magnus effect depends largely on the velocity of the spinning object, you may find that when upgrading to a DMR level of FPS you will have too much HOP effect, even when using heavy BBs. If this is the case you will need a harder rubber. For standard AEGs firing at around 350 FPS or under, a 50 or 60 degree HOP is what you will need, as any higher may see your HOP effect reduce. If you are upgrading your AEGs hop, the hardness of HOP rubber you will need depends entirely on what you aim to achieve with your setup. The following list outlines the requirements for approximate rubber hardness to match setups firing at a range of FPS.
Recommended HOP rubber hardness / Velocity combinations (0.2g BBs)
To get the most out of your Airsoft rifle you will have to set the HOP unit for the BB weight you are using, ensuring a flat trajectory and thus maximum effective range. In order to adjust your HOP unit, you will need a minimum of 30 meters safe range to shoot, either on your own property or with the property owner's permission, out of public view. Preferably this should be carried out when there is little to no wind, to make the job easier. Of course, you will need the obvious, BBs and eye protection.
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The first step will be to load your Airsoft gun with the BB weight you intend to use for Skirmishing, point it downrange, and shoot, paying attention to the trajectory of the BB. If the BB suddenly arcs downwards during its flight you have been a victim of gravity, and you need to increase the HOP effect by dialling your HOP unit upwards (some units are marked with +/-, others it will be trial and error). Once this has been done, fire again and observe the trajectory. If the BB now flies upwards, you are now shooting a mortar and you will need to back down on the adjustment. If the BB flies straight and flat, you have achieved a flat trajectory and thus, a perfectly set HOP up. Repeat this process until you have a nice, flat trajectory, and your Airsoft gun is ready for combat.
So perhaps you are wondering what we prefer to use in our own Airsoft guns? Sticking to a standard AEG sub-350 FPS setup, my personal preference in bucking/rubber is Guarder Clear 50 degree HOP buckings. These buckings are my preferred choice simply because they have been around forever and have always served me well. Being made from softer rubber, these can handle cold weather without losing too much performance, are decently robust and last for a good length of time, and are fully compatible with the vast majority of nubs available, though Guarder does include a basic soft nub with the bucking itself which works perfectly.
With a Guarder bucking installed I have always been pleased with my AEGs range and consistency, and have found they perform much better than stock HOP rubbers on more affordable replicas and are about the cheapest effective upgrade for AEGs available. As far as nubs are concerned, I prefer to use H style nubs, as I have found they offer a good balance between consistency and reliability. Whilst they may not provide the performance a Flat HOP or R-HOP are reported to have, I have had no issues with jams or compatibility. Since the design is well within the parameters of the original AEG nub design you can drop an H nub into your HOP unit without any risk of having the window in your barrel be too small, or your rubber being too inflexible. That and they require far less care and maintenance than Flat and R-HOP nubs, meaning more time shooting less time messing.
As far as replacement HOP chambers/units are concerned, I am currently using a ProWin AR36 CNC Hop unit in one of my many G36s, and it is performing nicely, providing a slight FPS increase due to the improved air seal from this precisely machined unit. I bought this to replace a unit I accidentally broke during disassembly, and though I generally don't upgrade the unit itself in my guns, I found that the ProWin CNC Hop unit provides enough improved performance and consistency to justify installing in a replica you want to get the absolute best from, particularly if you are building a DMR or other accurized setup.
There you have it! Our guide to HOP-up, what you need to know and how to get the most from the HOP inside your gun. This applies primarily to AEGs, though the principle is the same across all Airsoft Gun types. A more detailed guide to HOP disassembly and installation of rubbers and nubs is yet to come, so until then, good hunting!
Probably the best way to tune an airsoft gun at the beginning is to change its hop-up bucking. This is a relatively simple upgrade that usually does not even require us to break the service seal of the replica, which does not deprive us of any warranty. Of course, the details vary depending on the specific case, so it's hard to speak generally here. However, there is no doubt that even novice service technicians start with this system.
The problem arises at the stage of selecting the right part for our requirements. Hop-up bucking are built in different standards depending on whether they are dedicated to AEG or gas-powered replicas. Apart from these two standards, there are basically no others, because even sniper replicas use one of these solutions. Generally, it can be said that these two types of bucking coincide with the corresponding types of inner barrels. Paradoxically, those for GBB replicas are more often found in sniper spring replicas, but that's a topic for another article. In addition to the shape of the rubber, its other parameters are also important.
Before we delve into why manufacturers use different types of materials to produce the described elements, it is worth answering the question why they should do it at all. In fact, when it comes to spinning the BB, it probably doesn't matter what we do it with. Well, not necessary. It matters quite a lot. When choosing the right hardness of our rubber, we must answer a few questions.
How heavy BBs will we be using? Basically, the heavier ones require a harder compound from which the hop-up bucking are made. These are not very high requirements. It's not that slightly heavier BBs will require a much harder spinner. But the general rule is just that. This is mainly to minimize the wear of our rubber. Heavier BBs put more pressure on it and can wear it faster. Personally, though, I don't pay too much attention to it. This is important, but in times when the rubber itself is not too expensive and its replacement is not complicated, shopping aimed only at extending its life is pointless. Besides, I haven't managed to get the BB booster completely yet. I replace these parts more often because I want to try something new. But that may be my special case.
Above: Eraser HU THO-R for AEG / HPA / GBLS replicas
What is the power of our airsoft gun? As with the weight of the BBs, the higher it is, the harder the rubber we will need. This time, in my opinion, it is worth taking it more into account and not using bucking dedicated to weaker replicas to the stronger ones. This is where the gradual descriptions of the rubbers used by the manufacturers come to our aid. As a general rule, the higher the value, the harder the rubber. For assault airsoft guns of a kind, the golden mean is those with a hardness of 60 degrees. It doesn't hurt to go a little higher or lower than this rule sometimes, depending on our needs.
Under what conditions do we use our airsoft gun? In winter or generally at lower temperatures, we will need a softer BB. The material from which they are made most often hardens as a result of low temperature. For replicas that we use in winter, it is worth considering using a softer compound.
Once we know what our requirements for the hop-up bucking are, we can think about what material to look for this part. Basically, in airsoft we have two main raw materials that are used for production. The first are various types of rubber compounds and the second is silicone. Both of these materials have their advantages, but they are also not free from disadvantages. Depending on what we care about, we can choose one of them.
Silicone rubbers of their time were very popular. They were a hot novelty that everyone wanted to test after years of working with boring solutions based on rubber compounds. Their indisputable advantages include resistance to cold and softness. Even in sub-zero temperatures, they can retain their properties and spin the BBs well. They are also, one might say, stickier. The point is that even soft rubbers spin up heavier BBs well. This builds their universality. Unfortunately, they are not very durable. They don't last as long as other solutions. What's probably the worst is that they are very delicate to assemble. I ripped the first few silicone rubbers just trying to install them in the replica. I know I'm not the only one who has done this. They are certainly a good proposition for people shooting in colder climates and for snipers who need a good, strong spin even for heavy BBs. They will not appeal to people who expect durability.
Above: hop-up bucking included in R-Hop N24 Gen 2 kit
The second group consists of rubbers based on rubber compounds. And here, in principle, one could venture into far-reaching distinctions. Each manufacturer has its own special blend. This is more emphasized than in the case of moulded silicone parts, because here sometimes you can see the differences even with the naked eye. For example, the company Psionic, already described on the Gunfire blog, uses a mixture of polyurethane materials, which makes their rubbers transparent. As if they were made of silicone. Other manufacturers experiment with different hardness of the material. The biggest disadvantage of these rubbers is that they are often simply too hard. They are not suitable for weaker replicas or lighter BBs or become completely unusable in winter. Hence the popularity of models that, despite being made of rubber, are relatively soft. Their greatest advantage, in turn, is their resistance to both assembly stress and the ability to withstand high mileage.
Choosing the right hop-up bucking is not an easy task. It is difficult to point to one universal part that will serve everyone. It is therefore worth seeking the opinion of people who have tried before us and can talk about their experiences. Additional points if such a person has the same airsoft gun, inner barrel and hop-up chamber as us.
If you don't know where to start and the advice found on the Internet doesn't convince you, then unfortunately you can look for it yourself. It is worth starting with a rubber made of polyurethane plastic with a hardness of around 60 degrees. We can try several different producers. If we are not satisfied with the parameters, it is worth considering why. If the overclocking is too weak, you should look for a softer mixture. If it's too strong, you can think about a harder one. Over time, like many players and servicemen, we will come to a favourite solution.
Author: Boreq
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