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Old 10-08-2019, 11:09 AM   #1
wyz2285   wyz2285 is offline
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My recent findings

After the recent post about R-hop I went to record some videos for the tutorial. I also went a bit further to take some experiments and numbers with my friends.
First I drilled through a BB, ran a string through the hole and hang it in the middle of a clear tube, bored out a blowgun nozzle to match the typical airsoft nozzle then blew through the tube at 100 psi. Not as high as necessary to launch a bb at useful FPS so IRL the air current would be stronger and violent. I recorded the result in slow mo and as expected, the bb self-centered instantly by the current. Which mean if there is enough air, at least without backspin, a bb flows in the barrel. Which also means, specially for HPA systems where air is plenty, a non tight bore could have advantages.

Then I blew smoke through both ported (including ML CJ) and non ported barrels. None of them can produce laminar flow at the airspeed required to launch the bb. If you blow slow enough, both will produce laminar flow (straight smoke). ML CJ shows no smoke bleeding out from the ports, so I firmly believe you could cut out the crown and have the same results.

Joule creep. As long as you have a hop up, it will happen. Depends on your likings, r-hop can be a terrible choice. My friends VSR with AA piston, cut M130 spring and 300mm AA barrel, chamber and ML bucking produce 2J with 0,43 while mine with cut M170 produce 2,5J with 430mm r-hoped with the same bbs. However mine produce far more FPS with 0,2 than his. However mine sounds sweeter and is more consistent but I'm not here to talk about that as the rifles can not be compared. Just confirming that you can achieve useful energy output with ridiculously light springs, by using heavy bbs and bucking that require more pressure to lift the bb.

Pressure spike. It's most useful with a tight bore as little air passes through the side of the bb, it would dramatically increase the energy output of a short barrel, with a system which releases the air slowly (Mancraft in general, Wolverine single solenoid systems, long cylinder with weak spring). With Mancraft you can gain more than 50fps by just switch from a 300mm barrel to a 430mm. The hard data I have proof the pressure spike is a good thing, but I looking forward to test a system with long barrel and long r-hop to see if a more gradual acceleration is better.

My Imgur with some photos of the hop up system I'm developing and other stuff: https://imgur.com/user/wyz2285/posts
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Old 10-08-2019, 12:16 PM   #2
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Absolutely awesome!!!! :)
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Old 10-08-2019, 03:54 PM   #3
Sodium   Sodium is offline
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Im ordering a new barrel from edgi in a day or two. You just inspired me to add a short 7mm id barrel to the order to see what happens. (Im going to ask if he can add a very large id barrel to my order, and do it cheaply by lapping it very minimally (theoretically, if its centered, the finish MIGHT not matter much at all)). I'll post my results when it happens. (Not sure if 7mm is possible. Ill just go as wide as possible while maintaining structural integrity of the barrel)
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Old 10-08-2019, 04:03 PM   #4
wyz2285   wyz2285 is offline
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It will work, provided your system can produce enough air to maintain a large chamber to barrel ratio, either by making it short or HPA powered.
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Old 10-08-2019, 04:27 PM   #5
Sodium   Sodium is offline
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We are going with a 250mm barrel on a spring vsr-10
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Old 10-08-2019, 04:40 PM   #6
wyz2285   wyz2285 is offline
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I hoped you were using HPA. The 1mm difference is phenomenal specially with heavy rounds. I don't have the numbers but I have seen tests regarding 0,5mm increase in barrel ID can lower the fps by >50 give or take.
But it's your money and I absolutely looking forward to your findings if you did proceed.
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Old 10-08-2019, 05:15 PM   #7
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Im hoping I can get the barrel at a heavy discount because of minimal lapping. I may also put a stronger spring, and optimise piston weight. I dont mind spending hopefully only an extra $30 for something that may be revolutionary.

Last edited by Sodium; 10-08-2019 at 05:17 PM.
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Old 10-08-2019, 05:26 PM   #8
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If you want to toss another wrench into the numbers, try different nozzle bore diameters. In theory, it should affect the numbers similar to how pressure spike does. Though I suppose the catch would be that I am not too sure if different VSR cylinder heads have different bore diameters...
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Old 10-08-2019, 05:38 PM   #9
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With the 7mm barrel, your best bet is to get the bucking to hold the bb for longer. This will create the back pressure you need to get higher fps because you will struggle to get high with such a large gap between the bb and barrel.
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Old 10-08-2019, 05:39 PM   #10
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I did try smaller nozzle when I was testing the bb in clear tube. With a 2mm nozzle I can "control" the position of the bb by directing fast air flow. Per example, if I point the nozzle upwards, the bb will stick to the top. So in theory a misaligned smaller nozzle can make the bb start flying at different initial vector. However given the normal nozzle size it won't happen therefor no need to worry.
The problem with the bucking lock method is the bucking keeps the bb at the bottom, not centered. Although my test suggest the bb will self center almost instantly, my bb was static. I'm unsure if it will self center within the short barrel, I'm more inclined at it will.
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Last edited by wyz2285; 10-08-2019 at 05:44 PM.
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Old 10-08-2019, 05:41 PM   #11
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Quote:
Originally Posted by whalesmash View Post
If you want to toss another wrench into the numbers, try different nozzle bore diameters. In theory, it should affect the numbers similar to how pressure spike does. Though I suppose the catch would be that I am not too sure if different VSR cylinder heads have different bore diameters...

Bore diameters are easy to change. Fill up an air nozzle with 2 part epoxy glue and then drill it out to the desired diameter. Start off small and work your way up to bigger.
I might even be keen on doing this. It may also be useful in a high fps DMR.
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Old 10-08-2019, 06:09 PM   #12
wyz2285   wyz2285 is offline
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It probably won't do any good. The bucking lock does not restrict flow, once it releases the bb the bb has full flow behind it. A smaller nozzle however will just slow the piston down, not a sudden release of potencial energy. Think of it as an air brake as long as the cylinder.
The fact the bb self centers does bring an interesting thing, the LRB. Unless the bend is real sharp (which from what I have read they don't, just a couple mm at the tip) I do not see the bb touch the barrel. Specially LRB was mostly used before existence of hop-up. I have not idea how it could have worked and I will remain skeptical until I see it working with my own eyes.

Last edited by wyz2285; 10-08-2019 at 06:13 PM.
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Old 10-08-2019, 06:32 PM   #13
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LRB do work. I have made a number of them and you only need to alter them a couple of mm to see the bb start to fly higher.


The idea with the smaller air nozzle is that it does not create the pressure spike that a normal air nozzle does. So the bb stays for longer in the bucking and the pressure builds up behind it. If the bb can stay for long enough, the pressure will build higher than what it would have with the pressure spike, giving more fps.
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Old 10-08-2019, 06:56 PM   #14
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I don't have a definite answer as to whether wider bore nozzle or tighter bore nozzle would result in more joules with a certain setup. What I can say is that (at least for HPA engines) it makes a very large difference, with the most prominent example being the red nozzle on the fusion engine. With the setup I'm running on that FE, it only has a 210mm inner barrel and still regularly clocks over 1.6J even on the lowest dwell settings and 70 psi (basically as low as I can run it). It's also running an ERhop so it has very little pressure lock. Not sure how well this information would carry over to a VSR since it's a very different system (unless it's running an overvolumed mancraft bolt or something)
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Old 10-08-2019, 07:11 PM   #15
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Your clear bore test doesn't take the backspin imparted on the bb by the hop up into consideration. This, in my opinion, nullifies that test.
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