Black Fox's Tricks of the Trade - The Golden Secret

Discuss battery powered AEGs (Automatic Electric Guns) in this forum.

Postby Moparspanky » Wed Jun 09, 2010 10:27 am

If two bb's of the same weight leave a barrel at the same velocity they should have the same travel distance, theoretically. If they don't then something is putting another force on the bb that causes drop in velocity more quickly. The way I read this potential sticky is that proper matching can result in more velocity, which should be the only thing effecting range.

"As a result, the remaining air is wasted energy and the BB does not reach its full speed potential because the transfer of energy was not complete. The reason full cylinders are used on long barrel guns such as an M-16 is because the long barrel gives the BB more time to reach its maximum speed."

This implies that you will achieve higher velocity, and thereby longer range, which makes sense.
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Postby Blizzard » Wed Jun 09, 2010 11:02 am

Once I get my hands on a P90 and a Chrono, stay tuned for a full report. I want to see if this actually works. That former might be a bit harder than the later though...
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Postby Black Fox » Wed Jun 09, 2010 11:32 am

DMitri wrote:I'm only contesting the implication that too much air volume in a cylinder will cause a replica to be out-ranged by another replica with a volumetrically smaller cylinder in relation to the port, but that still manages to produce the same velocity regardless. This makes the only variable the volume of air, making your claim appear to be that too much air is detrimental. Without data this is hard to rationalize.

It could very well be true that the velocity will change between the two as a result of a plausible millisecond of increased resistance on the piston. The increase in velocity would, by extension, increase range--and even accuracy to a lesser degree. If that were the case it makes sense for Tokyo Marui and the like to include them in their replicas. But given that we have an artificial cap on velocity anyway--which is commonly reached, the argument appears moot to me.

Is it not also feasible, that if the time the piston travels were actually negligible between the two replicas, that it would result in greater air/bb velocity with the same energy needed to cycle the replica, given the amount of air in the cylinder is greater but still is compressed into the same amount of space in the same amount of time? I believe this is the concept behind "bore-up" cylinder setups. This would suggest that an unported bore-up cylinder set in conjunction with a tightbore inner barrel, would be the best first step to reaching the velocity cap, in order to lessen the requirement of the spring which increases strain on numerous parts and overall energy consumption, along with reducing rate of fire.

Data, my friend--it's crucial.

To look at it from yet another perspective, I said a long time ago that I'd be interested to figure out the affect that a ported cylinder has on the longevity of the o-ring, especially in replicas which also have ported piston head, along with other issues like expelling grease.

So, for the time being, for all the reasons listed above, I offer my own hypothesis that an unported bore-up cylinder is the best route to take for all replicas which are headed for their velocity limits, and possibly even without that requisite.


I hear you DMitri. I don't blame you for wanting to see hard data. If I didn't have a wife and two little kids, I'd be in my garage right now pulling all my cylinders out and start testing again. Unfortunately any data I wrote down years ago has long been lost. However, one example that I do remember the details on was a friends Tokyo Marui AK Spetsnaz that I was working on. I had an M-130 spring and a stock barrel (229 mm). When I put a full Systema Type-0 cylinder in it shot around 370 fps. When I put a Type-3 cylinder in it, it shot nearly 400fps. That was almost a 30 fps gain! (With an Excel 0.20g Bio-BB). Now when I asked my friend who worked at Systema about this. His explanation was that if you looked at the Type-3 cylinder. The forward end of the port is almost in the middle of the cylinder. This mean the first half of the piston stroke had very little resistance since the air was bleeding out through the holes. Because of the low resistance, the piston was able to gain more speed and therefore was able to impact the remaining air after the ports at higher velocity which translated to higher fps. He said when a piston travels through a full cylinder, the speed is not the same through the whole stroke. As the piston move closer to the cylinder head it picks-up speed and reaches it's maximum speed just before it completes it's stroke. So when using a full cylinder on a short barrel like the Spetsnaz. The BB has departed the barrel when the piston is only half way through it's stroke. And since the piston has not yet reached full speed. The BB is not receiving the full amount of energy that the spring is capable of providing.

I will say that if someone is using a cylinder that is providing too much air is not as detrimental to a gun that is using a cylinder that does not provide enough air. The one that does not provide enough air causes a vacuum as nears the end of the barrel which slows down the BB. One having to much air is still gaining speed as it travel down the barrel. It just doesn't receive the maximum speed that the spring can provide.

To change the subject a little I also heard that ported cylinders causes the O-ring to wear out more quickly because the grease shoots out the port and/or because of it constantly rubbing against the edge of the port. I think there is some truth to it and using good cylinder lubrication can make a big difference. However, KM did make tapered cylinders that provided the same benefits as a ported cylinder but avoided the O-ring rubbing across an open port. I have one of these in my M-4.

If anyone want to try experimenting on their own. I would suggest getting at least one full cylinder and one ported one that matches the length of your inner barrel. (If you have a long barrel then use a full and a ported cylinder for an M-4 thing these are easy to find). Test it on your gun an post your results here. A couple of note though. One, use the same BB brand and weight with all your testing. Two, note the results for each gun separately. For example, if you have two M-4s and you have a ported cylinder in one and a full cylinder in the other. You can't combined the results. You have to try both cylinders in each gun because every gun performs differently unless the guns are absolutely identical.

Anyway DMitry, keep poking away. I think it's a good thing. I think we all would like to know the nitty gritty details that would squarely put this to rest.
Last edited by Black Fox on Wed Jun 09, 2010 12:02 pm, edited 1 time in total.
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Postby Mini-Marine » Wed Jun 09, 2010 11:44 am

OK I think I see what you're getting at.

The impression I got (and I believe DMitri as well) was that given the same FPS, the gun with the proper cylinder would get more range.

What you are saying is that with the proper cylinder is more efficient and will grant higher FPS with a given spring, therefore you can achieve cap FPS with a lower power spring, which will in turn result in less wear and tear on the internals.
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Postby Black Fox » Wed Jun 09, 2010 11:46 am

Caffeine and Rage wrote:DMitri, is it possible that the excess air from a full cylinder on an M4 barrel causes extra turbulence right when the BB exits the barrel?


I've heard of this too. But unless we have access to a high speed camera and can put smoke into the cylinder, it's going to be tough to verify that one.
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Postby Black Fox » Wed Jun 09, 2010 11:54 am

DMitri wrote:I also think such an affect on the BB would alter its trajectory/accuracy and not just the range, I can't really fathom how range would be affected at all otherwise, given


I have heard people say that it did affect their trajectory/accuracy for the better. Although I have never really tested this aspect of it. So I didn't mention it in my original post. I think that's what Caffeine and Rage was referring to about excess turbulence.
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Postby Black Fox » Wed Jun 09, 2010 12:00 pm

Mini-Marine wrote:OK I think I see what you're getting at.

The impression I got (and I believe DMitri as well) was that given the same FPS, the gun with the proper cylinder would get more range.

What you are saying is that with the proper cylinder is more efficient and will grant higher FPS with a given spring, therefore you can achieve cap FPS with a lower power spring, which will in turn result in less wear and tear on the internals.


Yes, that is one way to look at it.
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Postby DMitri » Wed Jun 09, 2010 12:13 pm

As the piston move closer to the cylinder head it picks-up speed and reaches it's maximum speed just before it completes it's stroke.


This is another aspect that I have a hard time with, as I can at least attempt to reason the possibility of this being both true and false.

The part of me that thinks it could be true has to do with resistance, but how much resistance does a 6mm opening with a .2g BB in it really cause compared to the relatively massive tension of the spring? Is it even going to be noticeable? Working on airsoft replicas gives me a false impression about the actual resistance involved, as my thumb isn't going to move, which is the purpose of using it to test compression anyway.

The part of me that thinks this claim might be bogus, has to do with the tension of the spring being exponentially reduced during the motion of the piston. And while my tentative understanding of inertia suggests that the piston may not significantly lose speed--if at all--I don't see the logic behind it gaining speed even after whatever resistance of the BB/inner barrel is overcome, because the energy being provided isn't being increased and I don't see it taking any measurable time to reach peak velocity given the seemingly meager mass of all the objects involved.

Someone needs to set up a microphone and recording software to see if the point the piston is released is distinctly audible (or visible on a waveform), and then measure the difference between the two cylinders in milliseconds. I think that would be the clearest way to measure it considering we both have different hypotheses about which variables have a bigger impact on the BBs velocity. Rate of fire won't work accurately either, because of the fluctuations in voltage of the airsoft batteries and draw from the motor. The more isolated we can keep the independent variable (the cylinder), the better.

If the speed of the pistons are the same, but the velocity is higher in the replica without a port, it would suggest I was right about the increased compression ratio increasing velocity--this could actually be true even if it the piston were to move slower.

If the speed of the piston with a port is greater and results in a higher fps than the other replica, it lends credence to your hypothesis.

Who knows, maybe there will be a distinctive pitch change during each pistons course that will help us determine when it reaches maximum velocity. That's probably wishful thinking, though. I can't really think of a way to validate or refute the claim I quoted with experimentation, save clear cylinders and high speed video.

This is truly a job for Mythbusters--either that or maybe Fasteen can come out and put us in our places, argumentum ad verecundiam aside. :P

Anyway DMitry, keep poking away. I think it's a good thing. I think we all would like to know the nitty gritty details that would squarely put this to rest.


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Check this out....

Postby Boots Guy » Tue Jul 13, 2010 11:01 pm

http://www.airsoftgi.com/product_info.p ... ts_id=6798

Watch to end of vid where Tim tests fps on all three rifles.

Interesting to see that Ares used the same full size cylinder for all three of their G36's. Notice the results? The longer the barrel the faster fps. It appears that the full type cylinders do match better to longer barrels.

Food for thought :) [/url]
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