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Discussion Starter · #1 ·
I'm mostly interested in this for a test bed rifle.
So actual field performance isn't that important to me.
Though it would be a nice bonus if things work out right.

Right, if I were to take a rifle (from here on assumed to be a VSR), port the cylinder to, say 30mm of linear volume and fit an 80mm crazy jet barrel (the calculator says that's 5.2:1), add a ~10mm airbrake (assuming that completely kills 10mm of practical volume, the ratio is now ~3.47:1).

What happens?
I want to try a stock, a heavy (60g), a super heavy (100g), and a super light piston in this rig, just to see what energy they can achieve with what cocking effort.

If we are assuming a VSR with a 90mm piston stroke, a 30mm compressible volume, and a cylinder barrel ratio of 3.47:1 then the rig should be capable of slinging a very heavy (.50g) with a massive pressure spike through a compact rifle.

What do I think is going to happen?
I suspect a very heavy piston, with a lot of room to accelerate is going to dump that tiny volume of air over the BB like a freight train hitting a tube of glue.
But I wonder if a very light piston could reach a higher velocity and do the same thing.

This is mostly based on an old thread Vindicare Assassin put up, but with some changes (not restricting the airflow through the transfer port) to adjust to my theories about airsoft vs airguns (we don't need to obturate a projectile to the bore).

Any ideas, input, etc.?
 

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I'd say go for it.
In my experience, 40-65 grams is the ideal piston weight for most powers with a 300-475mm barrel as it gives the highest power, so I would assume that will be about the best weight.
I actually tried a 113X6.01 barrel in my VSR(Wolverine BOLT HPA kit) and didn't like the results.
With .48g BBs and hop set flat I needed 200 PSI to get the BBs to 1.51J, which was very very loud, not very accurate, and a huge waste of air.
For reference, I use about 159 PSI with a 6.03X300mm barrel to get 2.81J, which is more accurate, quieter, and more air efficient.
Eventually I plan to upgrade to a 5.98X500mm barrel when I have lots of money to spend on EdGi stuff, but for now a G-spec barrel is fine.

So, I'd suggest that you use something more like 200mm for a barrel, and you should probably bore out your cylinder head as much as possible to get better flow and power, otherwise you'd probably get the same power as I got, but you'd be pulling an M220 spring.

From what I have gathered from Polarstar, Wolverine Airsoft, a tech at Novritsch, airgun guys like FX, Daystate, Anschutz, and maybe another one plus talking to lots of people I know : low PSI plus long barrel equals better accuracy than high PSI and short barrel.
It almost always means better for your gun, as you're not using a spring that makes your arm hurt and whatever else.
But, good luck with this, I'm curious to see what your results are.
 

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I’ve honestly had better results across the board with short barrel sniper rifles. That’s with a vsr and “short barrel” being an inner of 300mm or the well known .48 volume matched length of 370mm.

Granted I’ve tried SO MANY parts combinations with chambers, buckings, Rhop, nubs, spring, hpa, co2...I’ve still always had better consistency with short barrels. It’s either in my head or the theory is true that short barrels = less time for the bb to “bounce around”. Long enough to be efficient enough (achieve the power you want) but not too short that it’s using a crap ton of air. I’ve converted all of my vsr-10s to short barrel configurations. They either have a 300mm, 350mm or 370mm. EdGi or PDI, 6.00 or 6.01.

Out of the 7 (I think) vsrs I have, the hands down most accurate one is this setup:

Wolverine E Bolt
Pdi 300mm 6.01
Faceless r hop patch
Random red bucking
(contact patch removed obvi)
(The bucking is very thin, unlike pdi Nineball)
Maple leaf omega nub
TDC mod

At the end of the day ALL of these parts and mods we do MUST work together. There is just something about the parts in that gun that somehow works phenomenally for me. I let all my friends use that gun (who don’t play often) and it works a treat!!

D0D963D5-BE18-4A71-BE3F-83B022BAFCB8.jpeg
 

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Another thing that I forgot to mention is that no air rifles are bolt action that are spring powered.
They all have a lever system, be that a break barrel or cocking handle, so they can use a spring strong enough to give a high enough pressure and pressure spike to shoot a multiple gram lead pellet to 500-1300 FPS.

I think that you had better check out THIS GUY'S CHANNEL and look at his more recent videos as he ports a cylinder, uses a shorter barrel, and a heavy piston.

THIS GUY also has some splendid videos on the matter
 

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Discussion Starter · #7 ·
I suspect that the huge run up that the piston has could allow a heavier piston to be way more effective than in an unported cylinder.

You're probably right that a 200mm barrel is more viable, I have a 220mm & 250mm crazy jet in my spares box to try as well.

I do wonder if a traditional nub bucking (or a W-hold), would work better with a violent pulse of air, has that been something you've tried with a HPA rig?
 

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Discussion Starter · #8 ·
To be fair, a 12 ft/lb air rifle (UK legal limit) is putting out over 16 joules, the max I'm going to play with is about 2.3, the air rifle thread is an old one with some interesting ideas in it.
Though the differences between rifled pellets that need to obturate to the bore, and BB that that need backspin for stability is something to consider.

I'll take a look though I only speak/read English.
 

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I do wonder if a traditional nub bucking (or a W-hold), would work better with a violent pulse of air, has that been something you've tried with a HPA rig?
As far as a non rhop setup I had good results with a maple leaf Diamond 60° (I call them the OG black Diamond buckings) and a panthera nub. I think the bucking wrapper says “monster” but I’m not certain. That’s the combo I run now in my ghillie vsr, which I plan to upload more footage of by the weekend!
 

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I used to port cylinders years ago. This was before cylinder to barrel to bb weight ratios were a thing that we knew about.
So by porting a cylinder and getting the correct cylinder to barrel ratio or a little larger to be on the safe side, you can nearly get the same energy rate as a full cylinder and a long barrel. There is a little less energy but not too much. The difference is that in a normal setup, the piston starts of slow and pushes the bb through the barrel and by the end of the piston travel, the bb exits at it's maximum speed. The ported cylinder was different in that it let the piston accelerate and so gain a lot of energy and then start to push the bb.
The reason why you want weight added to the piston is so it does not bounce of the layer of compressed air. Too light and it will bounce. But also, too heavy and you will not get up to the maximum potential.

This makes me want to experiment with extra short barrels and extra long silencers.
 

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Well, I have a 405mm inner barrel on my SSG10, and I get very accurate shots from 250ft away. (I use 0.46g bbs)


I have a 303mm outer barrel. The extra inner barrel is covered up with a Novritsch suppressor.
 

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Discussion Starter · #12 ·
So by porting a cylinder and getting the correct cylinder to barrel ratio or a little larger to be on the safe side, you can nearly get the same energy rate as a full cylinder and a long barrel. There is a little less energy but not too much.
If you were to hazard a guess at the potential energy you could glean out of a usable short barrel?
Do you reckon 2+ joules is viable?

The difference is that in a normal setup, the piston starts of slow and pushes the bb through the barrel and by the end of the piston travel, the bb exits at it's maximum speed. The ported cylinder was different in that it let the piston accelerate and so gain a lot of energy and then start to push the bb.
It just makes sense to me that a piston moving quickly before before compression is going to do a better job than a traditional set up.

The reason why you want weight added to the piston is so it does not bounce of the layer of compressed air. Too light and it will bounce. But also, too heavy and you will not get up to the maximum potential.
That makes sense, though I wonder how much that bouncing actually matters.

This makes me want to experiment with extra short barrels and extra long silencers.
You should, I think it might be the next major breakthrough, or at least interesting fodder for thought.
 

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I suspect that the huge run up that the piston has could allow a heavier piston to be way more effective than in an unported cylinder.

I do wonder if a traditional nub bucking (or a W-hold), would work better with a violent pulse of air, has that been something you've tried with a HPA rig?
I think that this runs back to the "High PSI low volume-Low PSI high volume" quest I went on a few months ago, you have the same joules/outcome, but with advantages like sound, accuracy, and ease of use from the low pressure high volume.
So you'd probably just need a stronger spring to achieve similar result in the end.

I used the purple standard bucking from the Novritch SSP1 as well as a Decepticon 60* and got similar results, both kinda sucked.
This makes me want to experiment with extra short barrels and extra long silencers.
You are certainly welcome, but I think that you will find that they are only useful if you live in Italy, Japan, Ireland, or Portugal if you follow rules.
Still, should be interesting to see your results.
I'll take a look though I only speak/read English.
If you are using a computer you can use auto translate, which will sometimes give bad translations that are so funny that you forget why you are even watching the video.
That, or they will make you question your existence, or you may learn about whatever you seek, be that related or unrelated to what you were originally searching for.
It just makes sense to me that a piston moving quickly before before compression is going to do a better job than a traditional set up.

That makes sense, though I wonder how much that bouncing actually matters.
I think that in life in general, you want to find balance, which I would say goes for your piston weight, whichever gives you the highest joules with your desired BB weight.

I think that bouncing isn't exactly bouncing, probably more like acceleration, deceleration, and a dead stop as the air is causing too much resistance for the piston to overcome.
I would expect that the ideal weight is where you are a little past the point where the piston can maintain a speed, and then past there your power drops.
I would also expect "bouncing" to cause bad accuracy as it could cause worse velocity deviations, while a constant push would be more stable in general, possibly leading to better accuracy and whatnot.

Or you could just be like me and think about this while rarely touching your lonely spring while embracing the warm feeling of HPA
 

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Piston bouncing would also cause accuracy issues a little too as you would have less consistent air compression rates.
 

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I've always thought that shorter barrels are probably more accurate because the bb is out of the barrel when the piston strikes, causing it to not experience that huge vibration spike.
 

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Discussion Starter · #16 ·
Piston bouncing would also cause accuracy issues a little too as you would have less consistent air compression rates.
That makes sense, could one mitigate this with an unweighted piston and a large enough aperture for air to escape through.

That, or they will make you question your existence, or you may learn about whatever you seek, be that related or unrelated to what you were originally searching for.
Existential dread is my jam.

Or you could just be like me and think about this while rarely touching your lonely spring while embracing the warm feeling of HPA
Eventually I'll invest in HPA, probably an MTW or VSS Vintorez, but that's for the future.

I've always thought that shorter barrels are probably more accurate because the bb is out of the barrel when the piston strikes, causing it to not experience that huge vibration spike.
I suspect you're right, though how short is the real question? Obviously there will be diminishing returns at some point.

What base do I start with?
I've been considering the Cyma VSR 10, with a bull barrel base, and a muzzle thread adapter into a suppressor, to keep everything stable I'll also use barrel stabilisers.

I'll start my testing with a 250mm barrel, would that protrude beyond the bull barrel base?
Will the adapter even fit?
Is there anything obvious I'm missing?
 

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The CYMA is a good gun, but for this I would suggest building an SSG10 from spare parts, and get the following parts instead of Novritsch ones.
Action Army hop chamber
Whatever bucking
Whatever nub
PDI barrel base for 2 piece PDI barrel
PDI suppressor adapter for barrel base

This will give you a really good test gun and maybe even playable gun, and save you loads of money in the long run as it will be about $400 total while a fully upgraded CYMA would cost more and not have an aluminum receiver or whatever other parts that are SSG10 specific.

The 250mm barrel should stick out 140mm or so based off of my measurements.
 

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That makes sense, could one mitigate this with an unweighted piston and a large enough aperture for air to escape through.
Yes. A larger aperture would help.
 

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Discussion Starter · #19 ·
This will give you a really good test gun and maybe even playable gun, and save you loads of money in the long run as it will be about $400 total while a fully upgraded CYMA would cost more and not have an aluminum receiver or whatever other parts that are SSG10 specific.
£300 is a bit hopeful for Nov stuff in the UK at the moment, given Brexit and all, if I got down that route I'd likely go with the MLC338 or the new APS Barret for their advantages.

For now I'll probably take the cyma for now, I'll do mods where I can and upgrades where I have to, because I'm not made of money.
 

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Went to experiment and found a crappy Jing Gong cylinder to wreck. Only problem was that I have managed to make it into a good cylinder. Now all I have are WELL cylinders but no piston that will fit in them that gives a 100% air seal. So until one of my current good cylinders start to crap out, I won't be doing experimenting.
So if anyone else wants to, feel free to experiment with short barrels, ported cylinder and heavier piston weight.
Back in the day, when I use to port cylinders, I never fiddled with piston weights. Nor did I experiment with silencing the ported cylinders.
 
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