Black Fox's Tricks of the Trade - Air Tight
There are many areas of your gun that you can upgrade to get the maximum performance out of your airsoft gun. One area that is sometimes over looked is the air tightness of your gun. Every little air leak in your gun reduces the performance of you gun. You’ll be amazed that by sealing all your air leaks, you can increase your velocity by 50 fps or more depending on the gun. In some cases this may require you to put in a lower power spring! And in my book that is the name of the game. To get the most power out of your gun with the lowest power spring as possible. Because with a lower power spring. Your parts last longer and you’ll get more endurance from your battery.
So when you are upgrading, here are things you should check to make sure your gun is air tight.
O-Ring & Lubrication
Everyone pretty much knows that a good O-ring is the most important components that create a tight seal in your gun and that a bad O-ring is one of the most common causes for loss in velocity. And mostly everyone knows that lubrication is also important component to creating a good seal. But what most people don’t know is that not all lubrications are the same. Unfortunately, using lubrication is part science and part art. Weather and temperature conditions can affect how a lubricant can perform. With that in mind here are some general rules.
Do not use lubricants with mineral oils, since these tend to damage rubber O-rings by making them too soft or eating away at the rubber. Also, avoid using lithium grease. The lubrication properties of lithium grease tend to break down over a period of time and eventually they become gunky. It’s best to stick to silicon based oils and grease.
In hot weather, it’s better to grease type silicon and spray or oil type silicon in colder environment. There is also a silicon dry spray that I think works well in both hot and cold environments.
My personal preference is to use Tri-Flow spray in the cylinder and clear silicon grease on the O-ring. One nice side effect of Tri-Flow is that it makes the O-ring swell a little which helps the O-ring give a better seal but it doesn’t soften the rubber. I have also used molybdenum grease in the past too with good results. Molybdenum grease is great for gears but some people questions its use for rubber O-rings and would put this in the same category as lithium grease.
You will need to experiment a little as to what will work best for you and I know there are a lot of options out there but here are a few that I know works well.
In grease form: Tri-Flow, G&P silicon grease (clear), Tokyo Marui silicon grease (Blue tube), Lens Anti-Fog silicon grease for scuba masks (clear type only).
In spray/oil form: Tri-Flow, Tokyo Marui.
In dry form: Tri-Flow, Amsoil.
Once, you selected your grease. You will need to test the piston for air leaks. To do this, first attach the cylinder to the cylinder head if you have not already done this. Then put the nozzle on the cylinder head. Place the front end of the cylinder into your palm. Insert the piston into the cylinder. Then push hard and hold it there for a moment. If you have a good seal the piston will slide in a little then stop. If not, the piston will slowly or quickly sink in. If this happens, stretch the O-ring a little. If it still happens, replace the O-ring. O-rings can be found at your local auto shop. By the way, O-rings at the auto shop usually come in 3 colors, black, green and purple. The green and purple ones are a little bit harder than the black one but they do work. These are usually used on A/Cs parts in the car. Also, when you do buy O-rings, buy several since they tend vary slightly in size.
Piston Head
When choosing a piston head. Choose one that has vent ports on them. These are usually a series of 6 to 8 holes that go around the front end of the piston head. What this does is, it allows air to bleed past the piston head when it is being pulled back, thus allowing more air to fill the cylinder quickly. There by ensuring that the cylinder is filled with the maximum amount of air before the piston begins to move forward. This again can lead to greater velocity. Again this feature is pretty much standard on most airguns now days but not all.
Cylinder Head
Some people say that a cylinder head that is cone shaped vs a flat in the back provides better airflow and improves velocity. Personally I feel this is true but don’t if there is enough data to prove this.
Nozzle
The next step is the nozzle. It’s always good to check the nozzle. A worn nozzle can cause air leaks. If you have an old gun, I would just go ahead and replace it. When you do replace it, make sure you get one that has a little rubber O-ring inside the base of the nozzle. This O-ring will help prevent air leaks. Now days, it is almost a standard feature but I would still check. There are also some nozzles that have two rubber O-rings on the inside to create a better seal. However, some people think this creates extra friction on the tube that the nozzle slides back and forth on. So will it supposedly creates a better seal it puts more stress on the tappet plate. But I’m not sure if either has been proven at this point.
Hop-Up Bucking
Next to the O-ring, this is the second most critical component for creating an air tight seal and can potentially create a dramatic increase in velocity. It is also the cheapest and easiest fix to improve your fps. I recommend replacing your hop-up every two years, sooner if you are a heavy user or when ever you notice a drop in your velocity.
When you do replace your hop-up bucking, I recommend you by at least two different brands. Why? Because the measurements inside a hop-up chamber vary slightly and so do different brands of hop-up buckings. I’ve learned from experience that while one brand may work well in one gun, it may not work well in another. This also goes for the inner barrel too. Some hop-up bucking tends to fit loosely over the inner barrel.
Also, hop-up buckings are delicate. If you need to remove the inner barrel from the hop-up chamber, they can some times tear when you pull them out. So it’s always good to have spares.
When you put in a hop-up bucking there are several things you should do.
First make sure you put it on the correct way. If you don’t you may not get a good seal and your hop-up may not work well. Almost all hop-up bucking have a protruding grove on the inside. When you put it on, positioned it so that the protruding grove on the inside of the bucking slides into the cut grove on the out side of the inner barrel. This will help align the hop-up nub on the inside of the bucking to the cut square section of the inner tube. This will also make sure you get a good seal.
Next, coat the outside with a little bit of silicon oil. This will help it slide into the hop-up chamber so it won’t tear.
Last, once the inner barrel is in all the way, check the back end of the hop-up bucking to make sure it is seated properly. If you look at the back of a hop-up bucking it is tapered. This area is thin and can sometime bend or curl when it gets pushed in. If it does, air will blow out and around to the out side and create an air leak. When you look into the back end of the hop-up chamber, the hop-up bucking should look perfectly round.
One last trick, wrap up the back end of the hop-up bucking with one layer of white plumbers taper. This will make sure that there no air will bleed out between the inside of the hop-up bucking and the outside of the inner barrel. Do not wrap it too tight because it could twist the hop-up bucking, thus causing an air leak.
My favorite brand of hop-up buckings are Guarder (clear), Systema (black) and Prometheus (soft-blue/purple). I've also heard some good things about Classic Army too but that they tear easily.
Well that is pretty much all the tricks of the trade to ensure that your gun is air tight. If you take all these actions when upgrading you gun. You could potentially see a substantial increase in your velocity.
Trouble Shooting
The two biggest causes for loss in velocity is a bad hop-up bucking or O-ring. Always replace the hop-up bucking first as this is the easiest and cheapest fix. If that didn’t work, change the O-ring.
If you done that plus tried all of the little tricks mentioned here and have done everything right but are still having trouble with velocity. Then only 3 other things come to mind.
First, if you have a cylinder with a hole in it. Make sure the hole is closer to the back end of the gear box and not the front. I’ve seen people take gear boxes apart only to put the cylinder in backwards. That will drop the velocity for you.
Two, if you have a gun that has a removable barrel that slides out such as a M249. Make sure the barrel is pushed in all the way. On some guns it’s a very tight fit. And if you removed the barrel and don't push it back in all the way. Then you are creating a gap between the nozzle and the hop-up chamber and are not getting a complete seal.
Three, the gun is defective. With cheaper guns, you run a greater risk of the gear box not being properly aligned with the hop-up chamber, thus causing air leaks. In most cases this cannot be fixed.
