The Hop up Compendium!

Inari

A while back I posted up a thread on barrels, which dealt with a lot of the basics of what barrel to choose, and what they do. As the name suggests, this one deals with hop ups Same as before, this is by no means infallible nor comprehensive, but rather just a (hopefully) informative post to help those who are a little confused. As always, if you disagree with anything I've said, post away! Debate always helps



The hop up is easily the most over-hyped part/assembly in your airsoft gun; they are drummed up as being something mythical, and normally associated with things like 'pixie dust' when they work well. Remember that all the hop up does is apply backspin to the BB, and ensure there is no air leaks (or at least minimises it). There are more factors to accuracy than just "Stick a guarder clear in" which was the mantra for range and accuracy for quite a long time. As such it is key to understand what each aspect of your hop up assembly does, so that you can more effectively tweak and tune and end up with what's right for you.

There are several parts to the hop up:
- Chamber (housing for the inner barrel, hop up rubber and hop up nub - it controls how much hop can be achieved)
- Hop up rubber (this is the piece that contacts the BB and applies spin)
- Hop up nub (this piece is the intermediary between the chamber's hop up arm, and the hop up rubber)

Firstly, let's take the chamber - you want a solid chamber, that sits nice and tightly against the gearbox shell with as little movement as possible. This will allow the air nozzle to seal more effectively with the hop up rubber, and avoid FPS inconsistency between shots. Typically speaking plastic chambers seal better than metal ones, though they're not as durable - there's always a trade off!
Different guns have different types of chambers, and it is widely accepted that the wheel-based design (G36, P90, SIG etc) is the best. Unlike the slider types of the AK's, MP5's, UMP's etc and the cog-based of the M4's, SCAR, F2000 etc - you have a much tighter control over how much hop is applied, and it is much harder to go too far. Now that said, with a bit of time and patience, you can tweak virtually any hop up chamber into one with good overall adjustment, as well as avoiding the dreaded 'hop up creep'

You want the hop up arm to have a good range of movement so that you can more effectively tune your hop up setting; you can have no hop on, or you can have ultra hop which will send your BB's vertical. Obviously exaggerating, but you get the picture! As previously mentioned, if you spend a bit of time with your hop up chamber you can get it working a lot more effectively - you can trim excess plastic off of the cogs to ensure a better mesh (this removes the dead space in a hop up chamber, where you meet sudden resistance even though you're nowhere near maximum hop), and apply a small washer to the main cog which acts as a lock. On the hop up arm itself you can use the likes of epoxy putty to build up the arm, to give it greater reach - you can also ensure that it has a flat surface so that when it pushes on the nub, the force is evenly spread (which is then translated onto the hop up bucking itself.
On the slider and wheel based designs you're limited in effect to modifying the hop up arm to have more reach; there's very little you can do to the wheels/sliders themselves, though some people will use things like grip tape to avoid the arm from moving, or O-rings on wheel based designs to apply greater friction to again stop the wheel from turning when you don't want it to!

(Photos Left to Right: Slider-type (AK, MP5 etc), Wheel-based (P90, SIG etc) & Cog-based (M4, F2000 etc))

The hop up rubber itself is literally a piece of rubber that is responsible for the air seal between barrel and hop up chamber, as well as being the main proponent in acheiving backspin - it is the part that the BB must push through. They are available in different materials and also in varying degrees of hardness. The softer it is the more friction is imparted, but also negatively effects the air seal (this is why hard rubbers are recommended for R-hop setups). The harder it is the less friction is imparted, or more accurately the more energy is required to achieve the same level of friction (i.e. ramp up the power), but the air seal is far more effective. The reason why using harder hop up rubbers gives lower FPS readings in standard set ups is because there is a harder obstacle in the way of your BB exiting the barrel, so of course it's going to be slower. Harder rubbers last longer, and softer ones wear much faster (think about it like tyres - the softer they are, the quicker they get up to ideal operating temperature...but by that very same virtue it means they are going to wear out much quicker); thankfully hop up rubbers are relatively inexpensive as opposed to high quality racing tyres, so you can afford to seek absolute best

The different materials hop up rubbers are made out of have different properties, though there is a predominance of silicone-based rubbers used. Some are better than others, and it effectively comes down to how that rubber interacts with your chosen brand of BB's. This is more evident in DIY methods, such as custom flat-hop modifications, or in designs such as the R-hop where many have tried replicating the results with different rubber tubing; you can see that some are more fit for purpose than others. Off the shelf products tend to be more universal, though you will still find some will work better than others. It is critical to understand that just because you have success with one hop up rubber with one setup, does not make it arbitrarily the best. Remember that each gun has the same series of parts, which can differ ever so slightly in parts, or even in assembly, so the properties of one hop up rubber could exacerbate underlying problems (such as poor compression in the gearbox etc), or it can similarly play to the strengths of the gun. For the best results for each gun, you really need to try lots of different combinations, and go for whichever one worked best - there are no easy answers/solutions...just work. Of course, that's only if you're looking for absolute best...and not everyone is. Some people just like to have a part or two that are not standard so that they feel their gun is more "custom"

On the hop up rubber itself you will find a thicker piece called the mound; the mound is the area of the hop up rubber that sits into the barrel window and is pushed down into the barrel by the hop up nub & hop up arm. This is the piece that generates the friction responsible for backspin/lift. Too much and your BB's go sky high, too little and they won't go very far at all!
There are different styles of mound available, from the solid one-piece design from TM's AEG, to the two-piece style that KWA have popularised, or even the newer ones completely sans mound for commercial flat-hops. The thicker the mound, as well as the more solid it is, will mean it will last longer than thinner/weaker ones - however it may not have the same effect you're looking for. The likes of the mapleleaf/KWA/Falcon type of hop up rubber with the two fins for the mound can achieve better lift for shorter amount of time. The two fins will wear out much quicker than the standard mound design, and it will not necessarily stay accurate for the whole time - as the round count increases, you can end up prematurely wearing one side quicker than the other, which will result in an imbalanced backspin imparted on the BB's i.e. you'll see them whisk out to the left or right. It is not a problem limited to the two fin style, however it is exacerbated/more prominent. The single mound types have a breaking in period where they're typically not very good for a couple of hundred shots, and then they reach their sweet spot, and then consistency will drop off again until it's replaced...it's like a hair cut; you wait until it's that little bit too long, and get it cut that little bit too short to get the most out of your hard earned cash.
The moundless types rely on the hop up nub to apply as great a surface area to the BB as possible, thus increasing the amount of friction applied to the BB and improving range. The problems that can occur are numerous - if the barrel window is not smooth, it can tear the rubber alarmingly quickly. On top of that because there is no thicker mound, the lifespan of the rubber is shorter (though this is partially offset by the increased surface area) which again will affect accuracy sooner than you would like. Beyond that the problems are normally to do with the chamber - flat hops were designed as a DIY modification; everything was custom fitted to your barrel and your hop chamber. Attempting a commercial release is commendable, however hop up chambers differ vastly even among the same model in the same brand, so it is is pure luck on whether or not it's a drop in fit. As such, many people achieve less than desirable results as the modifications done may not have been too successful.

(Photos Left to Right: Standard hop mound, Two Fin type)

Finally you have the hop up nub; this is the tiny little piece that comes with all hop up rubbers, and should be thrown away in favour of more robust solutions. For our power limits you really want softer hop up rubbers, and softer rubbers come with soft hop up nubs - they're useless. In fact, they're worse than useless. Many of you will have noticed that the nub is normally a piece of soft rubber tubing. The nub is pressed on from the hop up arm, which transfers that pressure to the mound of the hop up rubber. If the nub is soft, then most of the pressure from the hop up arm will be lost into the nub itself rather than being transferred to the hop up mound. This is the biggest reason people would see range benefits from the likes of the Element H-nub etc, because it is a hard piece of plastic. The best readily available hop nub is a suitably sized piece of bic/biro tubing - it is the right width/size, and is certainly the right kind of strength. Using the likes of a H-nub or Bic-nub (the pen ink tube) will give far more backspin to each BB, however the trade off is that if you put the hop up on full, your gun will jam. There is no forgiveness in a solid nub - if it's on too much, there is not enough room for your BB to squeeze past.
There are of course other nubs available, such as the new fangled ones from Prometheus and Mapleleaf, designed for use with commercial flat hops or the two fin design, as well as the likes of Shredders Concave Spacer (which, like the H-nub, helps keep the BB's a little more centred for greater consistency). What you're really looking for is something solid that applies the greatest surface area, and if possible that will keep your BB's centred for improved shot to shot consistency.

(Photos Left to Right: Element H Nub, Standard Nub, Prometheus Flat Nub, Shredders Concave Spacer)

So that's what each part does - not very confusing, is it? Brands want you to be confused - the less you understand, the more likely you are to buy their new miracle product which does everything you want it to do, for the low-low price of $29.99...the problem when you're aware of what each aspect does, you very quickly realise that there is little to no innovation in that area; it's all variations on the same thing. All you want the hop up to do is apply consistent back spin without any air leaking; that's it. So why are there so many products to choose from? Everyone wants something different, and most people shoot differently.

From here on out it is absolutely critical that you identify your own personal goals; what do you want from your hop up? Personally I try to keep my guns with a relatively flat trajectory with 0.25g BB's, choosing to compensate for longer range shots (more hop applied, aiming up etc), as opposed to having the gun set up for maximum range and compensating for closer ranges (aiming down etc). As such, that will obviously affect my product choice, as will your own personal tastes.

The Chamber
You want as much consistency as possible, and the greatest consistency is achieved through easier adjustment. Wheel based designs are some of the best - if one exists for your gun, get it. Virtually everything else hop up chamber based is a gimmick, whether it be the Airsoft Systems stop-on-empty, or Madbull's tracer module - they are additions to the main system of range of your airsoft gun.


The Rubber
If you're going for a DMR role, or maximum range role, then what you need is surface area - you want as much BB:Rubber contact as possible; the longer the better. This is why R-Hops work so well; the BB stays in contact with the rubber patch for much longer than a standard mound, and the consistency achieved is far greater than a standard set up. It also helps that the R-hop is not placed around on the barrel, but in the barrel; it is in effect grafted onto the barrel window, and the hop up rubber is then used purely for air seal. As such the BB cannot move the mound out of the way for the next shot even on high ROF setups.
For Irish power limits with a standard setup you are far better off with softer rubbers; 60 degrees is the hardest I would ever go - preferably 40 or 50. Remember to try out different rubbers with different barrels to see what combination works best for your gun.


The Nub
You want a hard nub for more measurable adjustment. With a solid nub you can more effectively gauge how much hop to apply, and have it more consistent than with the tubular style. The BB's have a much harder time of simply moving the mound out of the way, and as such your shot to shot consistency will improve. If you're looking for maximum consistency, go with the likes of the SCS (shredders concave spacer).


Why should I upgrade my hop up?
You should upgrade your hop up rubber only if you notice something lacking in your airsoft gun, whether that be shot to shot consistency, overall range, drop in power etc.
You should only upgrade the chamber if you feel that there is not enough overall adjustment, or if your chamber is damaged/leaky.
I would always recommend changing the nub to something more hard for more finite adjustment!

What parts should I choose?
- Wheel based design (where possible)
- Soft hop up rubber
- Hard nub (your choice if you want things like M-nub, SCS, H-nub etc)

...so there it is - that's my experience and knowledge on the matter. As mentioned before, it is not by any means comprehensive nor is it gospel, just decided to put it up and sure hey, you never know...might help clear the air a little for some folk

Kashkai

Perhaps a silly question but with regard to the air seal that the rubber provides, is there a danger that when putting in a tight bore barrel, the smaller diameter of this, even with the rubber installed, will allow air leaks from the chamber??

Inari

Prosperous Dave wrote: »

Perhaps a silly question but with regard to the air seal that the rubber provides, is there a danger that when putting in a tight bore barrel, the smaller diameter of this, even with the rubber installed, will allow air leaks from the chamber??

No such thing as a silly question!

The diameter of a tightbore barrel is only smaller on the inside. In fact most of the aftermarket barrels are thicker overall for this reason. It is evidenced by simple things such as the brass ring that comes with most standard barrels - the majority of the time this ring (which acts as a stabaliser) will not fit over the new barrel.

The reason why softer hop up rubbers leak more air than hard ones is because there can be more gaps/pockets between it and the barrel, whereas the harder ones are a lot more rigid. This is why a lot of people will use PTFE tape around the bucking (some use dental floss for more strength), as it holds the rubber tighter to the barrel. It does also make it thicker, so putting it back into the chamber can sometimes be tricky

dinnybyrne

Whats your favour rubber?

Inari

dinnybyrne wrote: »

Whats your favour rubber?

In AEG's I'm very partial to the G&G green hop up rubber; it's the one I try first if I'm not happy with the gun's current one. For pistols it's the Firefly extra soft; very good just quite expensive

Generally I'll try the G&G or SHS first, then onto the likes of the Madbull Blue/red and if they don't do it for me I'd move to the Prometheus purple. It has been very rare that I've had to go further than that to find a combination that worked best for the rifle.

dinnybyrne

Inari wrote: »

In AEG's I'm very partial to the G&G green hop up rubber; it's the one I try first if I'm not happy with the gun's current one. For pistols it's the Firefly extra soft; very good just quite expensive

Generally I'll try the G&G or SHS first, then onto the likes of the Madbull Blue/red and if they don't do it for me I'd move to the Prometheus purple. It has been very rare that I've had to go further than that to find a combination that worked best for the rifle.

Cheers for another great write up btw

Untamedlemon

That great Inari, it's things like this that i would've like to have read when I was starting off, would've been such a massive help. I said on your last thread like this that it should be stickied but honestly you deserve to have your own sub-forum if you keep going like this!!
Great work, massive help

CpcRc

Just to add a few things I've picked up.

There's also the a plus hopup rubber. It has a curved mound to conform to the shape of a BB better.
I have one that I have been meaning to test out but I am happy with my current setup.

My current setup is; Madbull phyton II tightbore, G&G green hopup rubber, Element h-nub, G&P metal hopup chamber and a spring on the barrel cut to length as it provides a better seal than the standard spring.

For standard M4 hopup chambers, after setting the hopup, you can sometimes use a precision screwdriver to tighten the screw on the adjustment wheel and this can be enough to keep the setting from changing because of gearbox vibrations, etc.

The dboys scar-L comes with a hopup chamber which looks remarkably like the madbull ultimate chamber. So it might fit other M4 aegs. Because it is dboys it might accept more hopup rubbers than the madbull one. The one in the scar-L came with a barrel spring for better seal but I'm not sure if the unit on it's own comes with the barrel spring. My dboys scar-L is probably my most accurate and farthest reaching stock hopup and barrel setup I have owned. Only problem with this part is that they are hard to find in stock online as I have had no luck trying to track one down for testing.

To tell when you might have to replace the hopup rubber by feeding issues;
If your mag is feeding but you can't feed BBs into the hopup chamber, even with the hopup turned off.
Your hopup rubber is too tough and the air nozzle cannot push the BB through the feeding lips.
This can be caused by the rubber being too hard for the energy of the aeg you're using (like Inari said, try to keep below 60 hardness).
Or this can be because your hopup rubber is old and it has dried up and hardened over time.
A fresh hopup rubber of a hardness rating suitable to your aeg's energy output

If your hopup chamber is feeding too many BBs and you are firing more than one BB.
Your hopup rubber is too soft or is worn and the feeding lips are too weak to stop more than one BB being fed into the barrel by the air nozzle.
This can be because you purchased a cheap hopup rubber that was too weak or had weak feeding lips or bought one that is too soft for the energy output of your aeg.
You can solve this by buying a better brand with higher quality feeding lips or a hopup rubber with a higher hardness rating if the one you had was too soft.

This is my second time writing this as I forgot to refresh this page after turning on my pc last time so lost my first response. I hope I didn't leave anything out.

Cheers for the write up Inari. Always looking for things to read on here to learn more stuff.

YbFocus

This stuff is gold for me, I know how to open a gearbox and work away on anything like that but its knowing what parts to get or what is better etc.
Thanks man, on my way to find your previous thread now, I vote for a sticky of this

Inari

CpcRc's post reminded me of something I didn't put in the OP:

How to test if you have an air leak

If you are concerned that you may have an air leak between gearbox (i.e nozzle) and hop up, then there are two very simple methods of testing it:

1.) Torch Method
Shine a torch down the barrel (with your gun fully assembled), and look in the feed tube. You should not see any light as the nozzle should be seated fully forward in the hop chamber. If you see light shining through, that's a space that air can leak out of

2.) Tissue Method
Turn your gun upside down, ensure it is clear of BB's, and place a small piece of tissue paper onto the feed tube of your hop up chamber. The tissue should rest across it, as opposed to being wadded up and placed inside
Cycle the gun a couple of times & observe; the tissue should not move - if it does you've got yourself an air leak.


Most air leaks between hop up and gearbox are caused when replacing the nozzle, changing the hop up rubber, changing the hop up chamber, and losing the spring on the hop chamber.

Each model of gun uses a different air nozzle, and not all brands use the same dimensions - some are longer than others (longer air nozzles in guns not designed for them will cause the gun to either misfeed, or not feed at all), some are shorter (shorter ones than designed for gun will cause an air leak), and others are fatter, or have a larger inner diameter (e.g. bore up). When replacing your nozzle, always line it up against the stock nozzle that came with your gun and it will be a lot smoother!

If you have recently replaced your hop up rubber and you've developed a leak, disassemble your barrel & hop, and inspect the rubber - it may have become torn in the process. If so, replace immediately. If the rubber is fine, wrap 1 full layer of PTFE tape (note: 1 layer of PTFE tape is where each loop covers half of the previous one, so that when you reach the end there is effectively two pieces overlapping all the way along) around the rubber over the barrel. Remember to stop before the C-clip section, or that won't clip in properly. Reassemble & retest.

If you've changed your hop chamber recently, it may not be compatible with the nozzle in your gun - it may need a longer one. Similarly, it may not be pushed back far enough against the gearbox shell - this can be achieved using a spring over the inner barrel, or simply by putting O-rings around the barrel. Both will achieve the same effect by moving the hop chamber back against the gearbox shell.

CpcRc

I didn't want to mention air nozzle problems as I didn't think it came under the hopup topic.
But yes, matching hopup chamber and air nozzle is vital. I suffered from an air nozzle that was too thin and short for a long time.

I would debate the torch method though, depending on the motor, the air nozzle will stop at a certain position each cycle.
This is due to how long it takes the motor to stop turning. In some cases this will mean that the piston will be slightly retracted as opposed to fully forward.

Some advanced mosfets such as ASCU and systema ptw mosfets have features to allow them to ensure the gearbox finishes with the piston forward.

I have aegs which do not have air leaks but will end a cycle with the air nozzle slightly retracted.

Of course you can always remove the upper and run it on full auto in a few short bursts until the air nozzle is fully forward and then test using a torch.

Personally I don't mind the air nozzle not being fully forward because I can then use a torch to see if there is an obstruction in my inner barrel or my silencer in't alligned properly and BBs might hit off it as they travel down the barrel

Edit: Almost forgot a tip about the c-clip. Some barrels will have the channel that's cut into them for the c-clip stop shorter than others. So you may have to remove a little bit of material from the ridge on the c-clip so that it can properly fit onto the barrel and keep it secure.

Inari

Aye, the nozzle will not always necessarily finish all of the way forward, however that can still cause a leak - for example in one of my guns if I had active breaking off, it was firing at 302-308fps (w/0.20g KA BB), whereas with active breaking on it was firing at 319 on the button (again w/0.20g KA BB).

Base Gun: G&P MRP-L
Set up:
- G&P V2 shell
- SHS 13:1 Gears (w/sector chip)
- SHS 15 tooth piston
- SHS Cut off lever
- AWS Raptor MOSFET
- SHS 8mm Bearing (glued down)
- SHS Air seal components (Cylinder, Cylinder head, Piston head, & nozzle)
- G&P Selector Plate
- Madbull Spring Guide
- M90 Spring (1.5 coils snipped off)
- SHS Neodymium Magnet high torque motor

Now I'm not saying it was a big deal - I would never have noticed it; the only reason I did was because I was fettling about getting the Raptor working, and I happened to chrono it. It was low, which I found odd as it had been firing higher, so I started looking for the reason why. Chrono'd with active breaking on and off, and found the difference (at this stage it was 0.81J) - so tinkered some more and got it where I wanted. Of course I was curious about the overspin, so chrono'd again and found that there was a 15-20 fps variance if the nozzle was retracted

The joys of not leaving stuff alone, eh? :P

CpcRc

I think one of mine shoots about 320 fps as is. So I don't think I'll tinker with it :P