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Discussion starter · #121 · (Edited)
I know Jeppe a bit and he's very methodical in his experiments and puts a lot of effort in these things, so I get where he's coming from.

Build a long gun (550mm barrel in a gspec or something), testfire, cut the barrel down, testfire. Speed will decrease (progressively more and more), not increase. This is the best way, as to not effect airseal, hopup setting, seating etc.
The funny thing is, this actually does not happen. Speed will increase (up until a certain point, then it'll start decreasing again). That's the whole point of cylinder:barrel ratios, finding the correct length to have the barrel precisely long enough. If it's too short, you'll lose efficiency, if it's too long, you'll lose efficiency as well.

There's lots of empirical data displaying this phenomenon, and while it seems counter intuitive, I have observed myself that excessively long barrels decrease muzzle energy (when chrono'ing with a heavyweight bb). With a .2 too, if the barrel gets even longer.

This only applies to springers/aegs because there is a cylinder with a certain volume. On gas or hpa guns this isn't the case (or at least, not for realistic barrel lengths).

The easiest way to demonstrate this phenomenon for yourself is to get an AEP with a tiny tiny cylinder and put a 500 mm barrel on it, that'll definitely show it haha :p

It's not really a thing if you're at a 400-ish mm barrel and changing the length by 50 mm or so. But if you make your barrel significantly longer than its optimal length (ratio/bb weight), then yes, muzzle energy does go down. Maybe it hasn't occured yet in your own tests, but it does happen ;)

God, I love ASF. This is one of the few places on the internet where you can have an actual proper discussion with both sides coming up with sensible arguments and talking to eachother like human beings, instead of just immediately resorting to calling names and such. This place is awesome :yup:
 
I already tested. I have build thousands of guns, altough not VSR's, and the pattern you indicate, i have not seen. "Barrel suck", in it's many forms, is a myth.
That is part of your problem. You have only experimented on AEG's and not bolt Action rifles. With an AEG once the piston has reached the end of the cylinder, the air nozzle retracts and allows air in the rear of the barrel meaning that there is little to no barrel suck.
With a VSR, once the piston has reached the end of the cylinder, the air nozzle stays in the bucking and does not allow air in behind the bb. This creates suction or an effect called Barrel Suck". So it may have been proven as a myth by people who do know what they are doing but I would not trust those people.

A heavy BB will not increase speed by having a shorter barrel installed in the gun, in my opinion.
That is also an issue. It is only opinion. Once again, I say, try some experiments yourself and you will have fact.

By the way my data has been put on Airsoft Mechanics and people were very interested and agreed with it. Google it.
 
Thanks Sven. I am sorry if i come across very absolute. I am challenging the core point, so i cut away the rest.

I guess where we're at is more test data on the table (be it previously done or new data). I may not have seen what you have seen if it is here; i am new on this forum.

At the moment, i don't have any really long barrels that i could throw away for proving a point (or disproving my own) in this thread, but if i get my hands on a barrel i will do so.
 
I know Jeppe a bit and he's very methodical in his
God, I love ASF. This is one of the few places on the internet where you can have an actual proper discussion with both sides coming up with sensible arguments and talking to eachother like human beings, instead of just immediately resorting to calling names and such. This place is awesome :yup:
100% in agreement with you :) being inactive some time from forum and damm did I miss it, fb or similiar isint proper replacement for this knowledge database. Also good discusions :shot: :cheers:
 
I love ASF. This is one of the few places on the internet where you can have an actual proper discussion with both sides coming up with sensible arguments and talking to eachother like human beings, instead of just immediately resorting to calling names and such. This place is awesome :yup:
Agreed. I enjoy this discussion. Even though it can be a little frustrating at times. But it is good.
 
Discussion starter · #126 ·
Thanks Sven. I am sorry if i come across very absolute. I am challenging the core point, so i cut away the rest.

I guess where we're at is more test data on the table (be it previously done or new data). I may not have seen what you have seen if it is here; i am new on this forum.

At the moment, i don't have any really long barrels that i could throw away for proving a point (or disproving my own) in this thread, but if i get my hands on a barrel i will do so.
I've got a pile of barrels leftover from all the stock guns I've torn apart, lol. If you want one to try it out, just let me know ;)
 
That is part of your problem. You have only experimented on AEG's and not bolt Action rifles. With an AEG once the piston has reached the end of the cylinder, the air nozzle retracts and allows air in the rear of the barrel meaning that there is little to no barrel suck.
PME is a common issue with longer barrels. FPS also goes down, but obviously not many stick around to measure the results when the piston goes zipper. This indicates that there is still energy to be delivered in a long barrel that there isn't in a short barrel. But that's an AEG cylinder/piston.
But how piston PME, Tappet PME, barrel length and SS plays together is a long, different discussion.

And i have build bolties :)
But only a handful or so.
That doesn't include the trillion cyma VSR's, m24's and WELL MB-X we've had through, which shoot 500-600fps out of box these days.

I looked for your thread on ASM, do you mean this one?:
http://www.airsoftmechanics.com/index.php?topic=12692.0
That is the closest thing i can find, but i don't see a chart, link etc.

I think what is important to define is if the "optimal barrel length" is where the energy plateous, or where it peaks. If it (effectively) plateous, then it is a "minimum" barrel length rather than "optimal" barrel length (ignoring the accuracy point atm). This is what we can see from your whole test data rather than conclusion alone.

Also for expirementations sake, i would include piston weight, or perhaps even do it 2-3 times with various piston weights. Or with different springs (M140, M170, M190).
Heavier piston evens out the pressure curve, and IMO it has a big enough influence that even without manual weight adding, it should be considered a factor. Since different pistons have different weight.

ASPUK released a 65gr piston recently, which, while heavier than what i'd use in 555mm, is an excellent "starter" heavy weight piston for shorter VSR's. Less than the 100-150g steel pistons.

But those test data multipliers...3 x Springs, 5 x barrel lengths, 3 x piston weights, for example. Is 45 disassemblies.
Times BB weights for chrono results.
 
While you all are on the topic of muzzle energy and barrel length, I have a question. If a BB fully accelerates, accuracy aside, does barrel length matter? If you measure the energy of a BB from a 500mm barrel or measure it 100mm away from a 400mm barrel does any discrepancy result? I assume the friction within the barrel is minimal so both measured energies at said distance should, in my mind, be equivalent.
 
While you all are on the topic of muzzle energy and barrel length, I have a question. If a BB fully accelerates, accuracy aside, does barrel length matter? If you measure the energy of a BB from a 500mm barrel or measure it 100mm away from a 400mm barrel does any discrepancy result? I assume the friction within the barrel is minimal so both measured energies at said distance should, in my mind, be equivalent.
To answer you question I'd say yes barrel lenght does matter especialy for heavy bb. Since we dont have ideal case one can not neglect friction inside barrel or air resistance, so if you run out of air inside longer barrel it will leave it with lower velocity.

If you meassure the same with 400 mm barrel and 100 mm away, velocity and thus kinetic energy will be again higher because you dont have 100mm barrel lenght of friction, you only have air resistance just like in the case of 500mm barrel minus added lenght for friction.
 
Discussion starter · #133 ·
It's not about friction: it's about pressure behind the bb dropping so low that the drag force in front of the bb is greater than the force caused by positive pressure behind the bb. Beyond this, the bb will only decellerate ;)
 
Hi !
I juste registered to post this message after I saw this discussion.
I did a big study in 2014 with AEG platform concerning the cylinder-barrel ratio, the results show that there is no constant ideal ratio. In fact the ratio changes by a factor of 3 on AEG. And changing the cylinder only can help you gain up to 100fps without changing the spring. These results seems to be verified on spring bolts, changing only some proportions. And are validated by a lot of players in the french airsoft community.
So I translated my study to help you customize your replicas ;)
You can find it at https://oioiairsoft.com/le-bon-cylindre-pour-le-bon-canon-etude/
Hope you will like it and pleased to see there is some other "airsoft scientists"!
Image
 
Hey man that's some really cool research, thanks for posting. I'm missing one thing though, what bb weight was used in the testing? This is a very important variable. And an other thing is how much does spring power affect everything?
 
Hi ! Thanks ;)
I only used 0.20 g BB's.
What do you mean by the the relation between spring power and ...?
Most people use heavier bb's than 0.2gm. On the sniper forums we prefer to use the heaviest bb we can get our hand onto (Also that the gun is capable of firing).
You will find that often, heavier bb's will have more energy than the light 0.2gm bb's and so we prefer heavier bb's. So experiments can be pointless if they are done with 0.2gm bb's.
What your chart does show is that longer barrels are better with 0.2gm bb's.
What about 0.3gm bb's or 0.25gm bb's? This is what most people use.
 
Most people use heavier bb's than 0.2gm. On the sniper forums we prefer to use the heaviest bb we can get our hand onto (Also that the gun is capable of firing).
You will find that often, heavier bb's will have more energy than the light 0.2gm bb's and so we prefer heavier bb's. So experiments can be pointless if they are done with 0.2gm bb's.
What your chart does show is that longer barrels are better with 0.2gm bb's.
What about 0.3gm bb's or 0.25gm bb's? This is what most people use.
My chart doesn't show that longer barrels are better with 0,2g bb's.
My post was only here to help you realize that there is no constant ratio to have the best efficiency contrary to what I read there. I did a long experimentation work, published and translated results for free.
It's not pointless, just an AEG study that will help comprehension of the particular relation between these two parts ;)

Well regarding spring power, the power of your spring also affects the optimal ratio. So with a stronger or weaker spring your numbers would change. I have no idea how much though.
Oh yes I see ! You are right ! The spring used for the study was the stock one, the replica was shooting around 320 fps.
A stronger one may have a faster decompression speed than a weaker one at the same time of the cycle, so I think it will clearly affect results for the smallest barrels. Maybe not a lot for longer barrels. It's only hypothesis, in airsoft there is so many popular beliefs that I only trust what has been tested... It would be particularly interesting to do another study with 3 different springs !
 
OMG!!! I wanted to thank you for de-mystifying this for me!!!

So here's my info:

Lancer Tactical LT20 (M82, AKA an A&K SVD cosplaying as a 50cal)
Bone Stock.

So I set it up, put on the sight, set the hopup and tested several weights of BBs. Ended up on .36... They shot the best. (Range, Accuracy, Consistency too.)

Tried .20, .25, .28, .30, .32, .36, .40, and .43... Landed on .36

So I put your formulas into excel, made a spreadsheet, and realized I'm in good shape up to a 650mm barrel. (Which I had ordered before I did this... LOL.... But it is a Prometheus 6.03 with R-Hop.... No 6.01 or Angel)

Both sets of numbers shown:
515mm (stock --> Guess what? Says I should use .36's)
650mm (planned --> Puts me into the inexpensive .25 and .30, exactly where I want to be!)

Thanks a MILLION!!!!!
 

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