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Old 10-08-2019, 08:19 PM   #16
1tonne   1tonne is offline
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Maybe while on the string, you could aim the air nozzle downwards to get it back spinning and then remove the air nozzle. You may see a pattern of it lifting to the top of the barrel.
Top be honest, it does not matter too much but I don't know if the bb travels the top, middle or bottom of the barrel. There is a good argument for all situations.
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Old 10-08-2019, 08:45 PM   #17
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Quote:
Originally Posted by wyz2285 View Post
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.
I don't particularly want to turn this into an LRB discussion, but I don't think our current definition of an LRB is the same as the originals that were used in the classics of the late 80's and 90's. As far as I can tell, they were never bent. Angled slightly, yes, but not bent; and I can't find any evidence that shows that the angle is actually what imparts spin to the bbs.

From my testing (using a custom chamber that replicates a traditional BV chamber) adding a bend to the barrel adds no perceivable backspin to the bb. The best I can come up with is that the offset OD on the chamber end of a traditional LRB is somehow forcing the bb through the upper portion of the front chamber o-ring thus imparting backspin as a sort of primitive fixed hop up. I have a feeling that the modern documented benefits of barrel bending is more due the bend stabilizing the bb better in the barrel (reducing bounce and/or barrel vibrations) and maybe reducing the chance of it impacting the bottom of the barrel (reducing the backspin when it impacts).

I have 2 Sheriff (the company that designed and patented the original LRB) LRB's, and neither are bent, but the one in my Crimebuster sure as hell shoots well. I'd love to understand definitely why... mainly because I want to replicate it and use it in my VSRs.
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Old 10-08-2019, 08:59 PM   #18
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They are bent in the last third of the barrel and it does create some type of updraft that makes the bb stay in the air for longer. Just like a bucking does. So the only logical explanation that I could see is that it is backspin that gives it this longevity in the air.
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Old 10-09-2019, 05:38 AM   #19
wyz2285   wyz2285 is offline
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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.
Why would that happen? The pressure lock should release the bb at same pressure levels, it's probably more energetic if the pressure build up is fast behind the bb given it will take a certain minimum time to overcome the friction of the bucking and bb weight, well a slower buildup just let more air leak through the side before the bb starts moving.
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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.
I swear the first thing I'm gonna buy once I get a better job is a high speed camera
Well at least it showed the air flow does something, it at least overcame gravity (bb didn't just stay at the bottom).

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Maybe while on the string, you could aim the air nozzle downwards to get it back spinning and then remove the air nozzle. You may see a pattern of it lifting to the top of the barrel.
that won't work, a spinning ball doesn't fly, it needs pressure differential. If I remove the air nozzle it would just spin; If I keep the nozzle downward to create back spin, the bb would stick to the bottom.
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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.
That's because FE has a massive main valve, that is piloted by a solenoid. Unlike other electro pneumatic HPA systems where the solenoid fires the bb directly. Therefor the minimum dwell is huge and not as responsive as a direct solenoid (not saying it's inconsistent). It is actually the best main valve in all the systems, just a bit overkill for airsoft. I use mine at 80 psi with 15ms dwell.
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Old 10-09-2019, 01:28 PM   #20
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I celebrate the push for a scientific approach, but I notice several issues on the methodology and conclusions.

Quote:
Originally Posted by wyz2285 View Post
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.
100 PSI is far more than needed to push a bb out. GBBs operation range lower limit is about 60PSI.

Quote:
Originally Posted by wyz2285 View Post
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.
I don't think anyone ever doubted the self-centering of a sphere in a tube. The real discussion is whether the backspin trumps the Bernoulli effect or not, which your test cannot answer as there's no backspin.

Also, concluding that a non tight bore could have advantages is a non-sequitur. You haven't tested with different bore diameters, and if you do the math, you'll see that the centering principle becomes much stronger as the barrel gets tighter.

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Originally Posted by wyz2285 View Post
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.
The whole point of crowning, porting, or the CJ sleeve is to work as the bb is exiting the barrel (i.e. when the main tube is plugged by the bb).
Anyone that has ever cut an inner barrel knows that you loose a lot of accuracy unless you get it re-crowned.

Quote:
Originally Posted by wyz2285 View Post
Joule creep. As long as you have a hop up, it will happen.
Joule creeping depends far more on the cylinder / barrel ratio and the piston type and weight than on the hop up type. You're looking at the wrong variables there

Last edited by Dimitri MdP; 10-09-2019 at 01:40 PM.
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Old 10-09-2019, 03:54 PM   #21
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Quote:
Originally Posted by wyz2285 View Post
Why would that happen? The pressure lock should release the bb at same pressure levels, it's probably more energetic if the pressure build up is fast behind the bb given it will take a certain minimum time to overcome the friction of the bucking and bb weight, well a slower buildup just let more air leak through the side before the bb starts moving.

AccurateDMD and I have both had an effect happen in our bolt actions when we added weight to the piston. Normally adding weight will lessen the fps because the piston will travel slower. But instead, we gained fps. (This is not JC). Our only assumption (yes we are guessing) is that the heavier piston allowed more pressure to build up slower and this gave us more fps.


I have also spoken to another tech who is very knowledgeable (been teching for about 20 years) and he also believes that if done right, a slower pressure build up can create more pressure giving more energy.


Any physics person able to confirm this? It would be good to actually have someone who has studied this type of stuff to confirm.
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Old 10-09-2019, 05:29 PM   #22
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To elaborate more, that slow build up in conjunction with the hop up holding the bb is increasing "backpressure" and ejecting the heavier bbs with more energy than you would expect with typical C:B ratios (assuming hop up is set to flat for bb weight or with the signature "flick" on the end everyone likes).

I agree with others as well. A lot of this testing is leaving too many variables out to really be worth drawing conclusions from. I'm not trying to bust anyone's balls, but I also don't want anyone to waste their time and energy. If this were simple to figure out, then the answer would already be known.

You're going to need more than a high speed camera to determine the outcome here when it comes to how a bb actually travels down a barrel after hop up is applied.

Edit: I'll also add that there is a point where increased weight on the piston reduces the power output on heavier bbs. I haven't done extensive testing, but I have found that typically, for maximum power output, the middleweight (aluminum) sleeve on the WASP is better. The steel sleeve typically reduces power on the heavy bbs, or at best, keeps it the same (while decreasing power and fps with lighter bbs as expected). When used in conjunction with an airbrake (yay more variables!) the aluminum again is king and the steel sleeve sees more dramatic power decreases at all bb weights.
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Last edited by AccurateDMD; 10-09-2019 at 05:44 PM.
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Old 10-10-2019, 05:50 AM   #23
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Quote:
The whole point of crowning, porting, or the CJ sleeve is to work as the bb is exiting the barrel (i.e. when the main tube is plugged by the bb).
Anyone that has ever cut an inner barrel knows that you loose a lot of accuracy unless you get it re-crowned.
I'm welling to bet if you seal the sleeve output with o-ring or tape, you will get the same result.
My opinion on heavier pistons produce more FPS is not duo to the slow build up, but the slower reaction: a light piston is to bounce once it reaches the air cushion created in the moment before the bbs is released, however the heavier piston will hold better it's momentum and hold that pressure longer.
I tested from 300mm barrel up to 500mm, with a custom carbon fiber piston (19g) up to a AA piston with weights, you will get a certain degree of joule reduction after switch to lighter bbs, given that you adjust the hop up accordingly.
Edit: After some extra digging on LRB, there seems to be other options, the Sheriff LRB offsets a straight barrel so the bb hits the barrel, gain back spin; another way as a channel cut through the barrel to create a fast flow to pull the bb to the top. So resumed it's just a really rigid hop up, same as Zeros r-hops. If you look at the numbers just a few mm bend the bb won't touch the barrel, but maybe the airflow is somehow modified to guide the bb better...

Last edited by wyz2285; 10-10-2019 at 09:54 AM.
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Old 10-10-2019, 05:56 PM   #24
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I would be surprised if a light piston bounces. In the bolt actions, we use some pretty big springs (M170,M190) that should easily push the piston through that backpressure. For it to bounce, the bb would have to stay in place for a long time creating a strong backpressure but I would think that the bb would have started to move before that type of pressure could occur.
It possibly could occur with a weak spring.


I guess with the long range barrel the bb may not touch the top but the extra air going under the bb still creates backspin. In any case, the more the LRB was bent, the more upward travel the bb had
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Old 10-10-2019, 06:55 PM   #25
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Yea, I'm a no on bouncing. The only time time bouncing (or suction as I envision it) should occur is in an AEG type system where the RPS is so high the piston is making its return before the nozzle unseals the bucking and the bb is still in the barrel. And most AEGs never get the type of 100% seal seen on bolt actions/have ported cylinders/etc.

There's no way any spring capable of producing more than 300fps will 'bounce' due to a less than 1 gram bb being held by a flimsy piece of rubber. It's hard enough to get the damn things into the cylinders when they haven't been under full compression.
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Old 10-11-2019, 06:06 AM   #26
wyz2285   wyz2285 is offline
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Not bouncing like a ball on a hard surface, more like a car hitting a bump. A heavier car will be less affected.
And yes they will bounce, which is more like vibrating. Even the piston on spring airguns do, and these are way tougher.
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Old 10-11-2019, 03:17 PM   #27
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But airguns also have a smaller hole and they have to push the skirt on the pellet to make them fit into the barrel (Shrink the skirt). So there is a whole lot of back pressure there.
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