All About R-Hops
There's recently been a few questions regarding R-Hops so I've endeavored to answer them as comprehensively as I possibly can.
So make yourself comfy, nip to the bog now then grab yourself a cup of tea: this is a long answer
I'm gonna give a quick intro on what an R-Hop is first, just so we're all definitely understanding exactly what we're talking about and anyone who doesn't know, can understand.
An R-Hop is a small patch of rubber that sits in the cut-out window of the inner barrel.
It slightly protrudes into the barrel in order to apply friction to the BB when it passes.
This causes backspin.
It differs from a regular hop system because it almost completely matches the profile of the barrel.
Aside from being a bit of a pain to learn how to effectively install it, that's about it really
As I said earlier, it's not a magic system that defies the laws of physics or some super material that will triple your range etc.
What it does allow, is the most efficient use of what's already available.
It builds upon existing systems and improves what they offer, albeit at a much greater initial cost in terms of installation time.
The way an R-Hop is installed is one of the main sticking points I often come across. Due to the varying tolerances of components used in Airsoft and the vast number of options we have when it comes to adjusting other performance characteristics; the installation of an R-Hop needs to be tailored to each individual set up a lot more than other hop systems.
This in itself, is a factor in why it can be more effective but not the only factor, or you’d be able to get the same results just by taking the same care with installing any other system.
For example, when most hop systems are designed or upgraded, the main question asked is: “how soft or hard a rubber should I use?”
A softer rubber will mould around the BB more, giving a greater surface contact area.
This greater contact area gives more friction, which in turn gives more backspin, and I’ll cover why this is important shortly.
The downside to soft rubbers is that they don’t hold their shape as well. They are more prone to deflection from the passing air and BBs, which causes inconsistencies; both in air seal and friction.
Harder rubbers will hold their shape much more effectively, giving far superior consistency. The downside to this is that they can apply much less friction and therefore, backspin.
When installing an R-Hop, you must not only think about the hardness of rubber you’re going to use for the best consistency, but also the length of patch and so the length of hop window elongation required, the inner and outer diameters of the barrel, the weight of ammo, the power output of the source (fps) and the type of hop chamber.
All of these things are factors in regular setups as well as R-Hop installations but while they are often thought about in passing in the former, they are required considerations in the latter.
A good R-Hop installation forces thorough consideration of the whole platform.
This does not make the R-Hop installation necessarily better but it does go some way to improving the way a tech might approach a build and, in an ideal world, should be required either way.
So maybe the biggest disadvantage to installing an R-Hop is the process of installation.
A lot of work is required to get one in and they are not the easiest things to work with, being so small.
The patch must be trimmed to length, height and sanded to match the inner and outer diameters of the inner barrel almost exactly.
The hop rubber must be modified to remove the internal nub which usually contacts the BB and the hop-arm must have the curved, external nub holders removed so it can apply even pressure to an elongated flat nub.
I know when I first started it took me around twenty installations to train any semblance of usable technique in to me. It then took another eighty or so installations to reduce the installation time from about three hours to around thirty minutes with less than a one percent failure rate.
I don’t believe this should be a barrier to performance though, which is why I always share any tips and help I can with those who wish to try it for themselves
Now that we (hopefully) understand what an R-Hop is and how it gets where it does, lets move on to the crux of the issue: how does it improve performance?
There are several main factors which determine the performance but they do not all boil down to what an R-Hop is, more than what it allows.
The first factor is backspin.
I’ll try to keep the jargon to a minimum but I would advise that the ‘Magnus Effect’ wiki is given a quick look over by interested parties who haven’t already done so.
When a sphere is spun backwards through the air, it creates lift above it. This allows our BBs to ‘fight’ gravity for longer than they otherwise would be able to. The amount of backspin required to give the ideal trajectory for a BB is mostly determined by the weight of BB; with heavier ammo requiring more backspin.
Our traditional hop systems are completely able to apply the required backspin for the most common weights of ammo (0.2 - 0.28g), so if judged by this factor alone, an R-Hop might not seem like much of an improvement. There are many other factors at play though, which can make R-Hops perform better, even outside their main ‘comfort zone’ of floating much heavier ammo.
The second factor is exactly how an R-Hop applies the pressure.
In a traditional system, you have a curved nub protruding into the barrel and when the BB passes underneath, it deforms and flattens out slightly. The backspin it applies can be imagined more like a backwards ‘flick’ on the BB.
An R-Hop applies the pressure gradually and evenly, meaning there are fewer variables and inconsistencies through excessive movement.
Another (theoretical but anecdotally proven) beneficial effect of applying the pressure like this, is that the BB leaves the patch much more smoothly, resulting in fewer bounces along the inside of the barrel.
The third factor is the centering of the BB.
When an R-Hop is correctly installed, there is a very slight protrusion along the whole length and breadth of the hop window, on the inside.
This allows the BB to touch not just a single point but a whole curve.
If your R-Hop patch is centered, then your BB is centered and when it leaves the patch along the barrel, it is much less likely to come into contact with the sides of the barrel.
The ideal scenario is that the BB travels straight down the centre of the barrel, without touching the sides at all. Any touch from the barrel will impart friction and therefore adjust the direction of spin from being exactly backwards to slightly to one side.
Traditional hop rubbers protrude into the barrel more in the middle and less to the edges. This necessarily holds the BB very slightly to one side, greatly increasing the chances of off-axis friction and is what gives you those annoying fly-aways at extreme range (or less depending on the quality of the setup).
An H-Nub or ‘fishbone’ spacer go some way to mitigate this; an R-Hop is just the logical extension.
The fourth main factor involved in the effectiveness of R-Hops, is that they do not need to protrude into the barrel as much.
I touched on this earlier: because the R-Hop patch is longer, it needs to protrude less into the barrel in order to apply the same or greater amounts of friction.
This allows the air pressure to transfer the energy more efficiently to the BB, resulting in less of an fps drop per amount of backspin. Of course, this effect must be taken into account when designing the build so it does not fall foul of any power limits.
The last main factor is the separation of the method of backspin from the air seal.
Tradition hop rubbers are single units which must apply backspin and seal against the barrel and nozzle.
This means a compromise must be made between the aforementioned levels of hardness. This compromise is most noticeable in high fps guns where a soft rubber is necessary to float the heavy ammo but much more likely to ‘blow out’ due to the lessened ability to hold it’s shape.
With an R-Hop, this compromise is no longer necessary.
The method of backspin has been separated from the method of air seal so the tech is free to choose the most suitable rubber for the given setup.
As you can see, there are a number of advantages to a properly tuned R-Hop.
Greater consistency, more backspin allowing heavier ammo; and better efficiency.
All of these advantages are evident when using common weights of ammo but they are further enhanced by using even heavier ammo still.
So why is heavier ammo better than lighter ammo?
An item with heavier mass will have greater momentum once it’s moving.
This means that when it’s going in a certain direction, it takes more effort to make it do something else. Wind and other variables will have a lesser effect
We all know that heavier ammo will have a lower fps in the same gun as lighter ammo but what is often not realised, is that the energy level at the muzzle is the same. So the heavier BB might be going slightly slower but it has just as much energy and because it bleeds off this energy slower (conservation of momentum), it will have more energy left at any given distance than lighter ammo.
Heavier ammo is more affected by Gravity which is why more backspin is required. It also takes longer to apply the backspin due to the weight and this is where an elongated patch really shines.
Not only does a heavier BB have greater forward momentum, it has greater angular momentum. ie. it takes more effort for the backspin to stop.
For example. a 0.2g BB can spin backwards (without massive overhop) at ‘A’ speed which will last ‘B’ time but a 0.4g BB can spin at ‘2 x A’ speed for LONGER than ‘2 x B’ time.
I understand that might have been a little more jargon than is useful so basically, what that means is that heavier ammo can fly further due to the speed bleeding off slower and fly further due to the backspin bleeding off slower.
This all assumes that you can apply enough backspin
Traditional systems cannot apply enough backspin for the really heavy ammo (0.32g+) without significantly blocking the window with material and dropping the efficiency dramatically.
There are also optimal weights for different characteristics of performance at different power levels.
You might want more range in order to suppress and not be fussed about accuracy or you might want pinpoint accuracy at the expense of a little range. Each of these would require a different weight and a slightly different set up of hop.
I have personally done some side by side comparisons of stock setups and different variants of R-Hop.
When comparing different hop systems, it’s important to note that only the source power level is important.
Different hop systems necessarily affect the muzzle fps and measuring that is part of finding the most efficient setup
My most recent test was with my High Cycle P90. This test measured the difference between complete hop assemblies, not just the R-Hop; although the main factor was the method of backspin.
I used two identical length barrels and the output fps (345) was very close with each one (within 15fps).
Setup 1: Completely stock Tokyo Marui
Setup 2: PDI 6.05 barrel, Prometheus Purple rubber, Prowin Chamber and an ER-Hop
Test 1: 65m range using 0.25s
Setup 1: Most shots within a 0.8m square
Setup 2: Every shot within a 0.7m square
Not really enough difference to justify the extra cost. If a customer told me they would only ever be using 0.25s, I would have advised against spending as much money, probably against any upgrade to the barrel at all.
Test 2: 65m range with 0.28s
Setup 1: Every shot within a 0.6m square
Setup 2: Every shot within a 0.4m square
Better results here. I would definitely recommend an R-Hop over the stock system but probably not the rest.
Test 3: 65m range using 0.43s
Setup 1: Barely reached 30m
Setup 2: Every shot within a 0.3m square
The first two tests were nowhere near the maximum range capabilities.
The third test was pushing the limit of the range with the second setup, probably slightly past what I would call it’s peak efficiency for range in that setup. But that’s a call that the owner or tech must make as to whether more range or accuracy etc is preferable (once you get into the extremes).
I’ll just drop in a quick note here to dispel a couple of the most common myths I hear:
-R-Hops are not magic
-They are completely adjustable
-They can work with any weight of ammo if set up correctly, you’ll just see more benefits with heavier ammo.
So a lot of what an R-Hop does, is just increase efficiency and take the current systems to the furthest logical end we can imagine.
The main effect of a lot of the factors I’ve explained is to increase the consistency. More backspin means heavier ammo which means more accuracy etc etc.
When you add up all of these little benefits, it equates to a big difference. By bringing in all those fly-aways you don’t necessarily add any energy or make the BBs fly a further distance, but they do fly straighter which means more effective range.
I suppose the simplest explanation, aside from allowing significantly heavier ammo to be used, is that in an otherwise perfect system, an R-Hop turns your Maximum range in to your Effective range.
In a less than perfect system, it brings everything up to scratch and does the same
There are probable a whole number of points I’ve missed (I’ve run out of tea now), so if you have any questions, just fire away and I’ll update this as necessary.