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Hey guys! good morning. Yes 1tonne thats what im asking :tup:. And thanks Reliku :tup:

@1tonne can you share the 450mm, 430mm and 410mm information? :yup:

I have found some maple leaf crazy jet barrels at this store https://www.airsoftatlanta.com/products/maple-leaf-crazy-jet-barrel-system
for sure ill buy one for my AEG one for my GBB pistol :tup: but im not sure yet what lenght :doh:

Thank you all again!
 
I would not get 450mm. It is too long. The longest you would really want to go is 435mm. This would be used with a 0.2gm bb. 410mm is about right for a 0.3gm. These lengths should give you the most energy for that bb weight.
To be honest though, it does not matter to much because once you go over the best length for the bb weight, the accuracy should still be reasonably good. The reason for this is that the air nozzle retracts as soon as the piston has finished it's travel. So there is very little to no suck back effect. So the lengths that I suggest only give you the most energy. Normally (not always) the more energy a bb has, the more accurate it will be.


I will post a thread on the forums sometime with a graph that I made from the data. It makes for some interesting info. It shows the barrel length that will give the most efficiency and also the barrel length that will give most joule creep. Note: The barrel lengths that give the most JC are ridiculously short and so I would recommend them as it is too hard to get good energy with those lengths. So as I mentioned earlier in this thread, I would recommend a barrel length of 160-170mm. This length is a pretty good compromise. You can then add weight to the piston if you want to increase the JC even further.
 
The longest you would really want to go is 435mm.
Seems like a general consensus is 430mm. That should be a cylinder:barrel ratio of 2.7. What if I get short barrel (303mm), then it would be 3.8 ratio. Isn't that too much? What weights would you use then? I can only get my hands on 0.49 and then they come in 555 count packages and very expensive, so practically 0.45 specna arms or 0.43g madbull are available to me. Am I chained to having 430mm barrel, because for all purposes 303 is just to short for bb weights available? What if you weighted down piston a lot in that setup? That would help? I'd really like to have as short barrel as possible.

Oh and I'm at 550-600fps
 
This is the barrel lengths you want with each bb weight for the best efficiency.

0.3gm bb use a 554mm barrel (15821 mm^3) = 2.26:1
0.32gm bb use a 530mm barrel (15136 mm^3) = 2.36:1
0.36gm bb use a 500mm barrel (14279 mm^3) = 2.51:1
0.4gm bb use a 470mm barrel (13422 mm^3) = 2.67:1
0.43gm bb use a 430mm barrel (12279 mm^3) = 2.92:1
0.45gm bb use a 400mm Barrel (11423 mm^3) = 3.13:1

So for 0.49gm I would advise about 360mm

Weighting the piston down will slow the piston down but increase joule creep. So you will lose energy. You will need to increase the spring size to counteract the loss of fps. So only do this if you need a JC rifle or you like a little recoil (not that it really makes much recoil at all)
 
This is the barrel lengths you want with each bb weight for the best efficiency.

0.3gm bb use a 554mm barrel (15821 mm^3) = 2.26:1
0.32gm bb use a 530mm barrel (15136 mm^3) = 2.36:1
0.36gm bb use a 500mm barrel (14279 mm^3) = 2.51:1
0.4gm bb use a 470mm barrel (13422 mm^3) = 2.67:1
0.43gm bb use a 430mm barrel (12279 mm^3) = 2.92:1
0.45gm bb use a 400mm Barrel (11423 mm^3) = 3.13:1

So for 0.49gm I would advise about 360mm

Weighting the piston down will slow the piston down but increase joule creep. So you will lose energy. You will need to increase the spring size to counteract the loss of fps. So only do this if you need a JC rifle or you like a little recoil (not that it really makes much recoil at all)
I hear you. I've read it a hundred times and then again, I just don't know what happens after you go over 3:1 ratio. Do the bb become unstable with so much air behind them? You've stated you cut barrels shorter and shorter and recorded data. What was the info/conclusion on short 303mm version? Is it fieldable? Does it just randomly spew out bbs due to too much air?
 
Shorter barrels are fine too. They seem to be just as accurate but you will not be getting maximum efficiency from your cylinder. So, if you want to go shorter, that will be fine. It is only when you go too long that there becomes an issue.
 
Shorter barrels are fine too. They seem to be just as accurate but you will not be getting maximum efficiency from your cylinder. So, if you want to go shorter, that will be fine. It is only when you go too long that there becomes an issue.
don't forget that the air coming out will be a bit louder. more air more pop
 
I’m interested in long range and accuracy and joule creep. I think before buying barrel, I’m gonna go ahead and try cutting stock one. I don’t have a chrono tho. Just’ll have to judge by eyes. I have 2 options for barrels: 430 ml crazy jet or 430/303 pdi raven steel 6.01. Any tips there?
 
Normally to get the most JC I use the barrel lengths that I have recommended. These barrel lengths use the entire piston travel length and get the most efficiency for the heavy weight bb (The heavier the bb, the shorter the correct barrel length is meaning it is less tuned for the 0.2gm which means you can get more JC). The next trick after this is weighting the piston so that in it's very first initial movement, it moves slowly which is when the 0.2gm bb starts to move and as the piston travels through the cylinder it increases speed. As it increases the heavy bb starts to move. So the 0.2gm has slow piston movement meaning low energy and the heavy bb has faster piston movement, as it exits once the piston just reaches the end of it's travel which is when it has it's maximum speed.
So, try adding weight to the piston by wrapping solder around it and hold it on with one layer of electrical tape. You will also have to use a bigger spring. JC tends to work better with higher springs.
 
Hello, thank You all for the knowledge, especially Reliku & 1tonne. The impact You guys make in VSR related topics is enormous.

I have a quick question regarding inner nozzle diameter? Does it affect the build in a wrong way when it's to small?

I use AA cylinder head with 3,5 mm nozzle diameter and no matter what spring I use (various springs from 430 to 720 FPS) I can't get the rifle silent with 0.50 BBs. Of course I don't expect to make it silent with over 700 or even 600 FPS but regarding the ratio, 430 or even 500 FPS should make it work? No matter if I shoot with BB or without it I still get almost the same flat bang which could be a result of air moving to slow through nozzle and not giving the BB all the potential it could?

Don't get me wrong. The loud bang is not a problem but only an indicator that something is wrong as I suppose.
 
The AA cylinder head is not the issue though you could always drill it out an extra 0.5mm or so.


What parts are in your rifle?
Cylinder?
Inner barrel diameter and length?
Cylinder head cushion? (Sorbathane)
Spring brand and strength?
What is your main bb weight?
Silencer Length?
 
PDI HD piston (regular, non bore up) + AA cylinder and AA cylinder head + PDI 430 x 6.01

Varius 13 mm springs but I focus mainly on 550 FPS so lets take ASP M150 and PDI 520 and they both give me 500 FPS with loose hop up or 540 with pressed bucking.

Tried different 0,40 to 0,50 BBs. No silencer, no cushion at piston head, no cushion at cylinder head... here's the problem? Should I ignore the bang and just trust the ratio?
 
Put some Sorbathane or foam (Sorb is better) on the cylinder head and piston head. That should help a lot. Currently you have 2 metals impacting which will create a big sound. It will also be very hard on your cylinder head threads.
Also, a silencer is very important even when you have the correct cylinder to barrel ratio. It will capture the excess sound.
 
Based on various threads here and elsewhere, I made a spreadsheet to calculate ratios, ideal bb weights and barrel lengths.

All you need to know as a basis is what your cylinder inner diameter is, and the length of the compression stroke, everything else can be calculated.

https://drive.google.com/open?id=1_ZkGx_l-1dOppvGsG9w7vEiVVOB1CI2co6JkO_1_JtI

Downloadable Excel file: https://www.dropbox.com/s/v6093fxjeme36h1/Volume and BB Weight Calculator by Sev (Excel).xlsx?dl=0

Lemme know if there's any issues as it's my first Google upload.
 
No matter if I shoot with BB or without it I still get almost the same flat bang which could be a result of air moving to slow through nozzle and not giving the BB all the potential it could?

Don't get me wrong. The loud bang is not a problem but only an indicator that something is wrong as I suppose.
Huge red flag.
There should always be a difference in piston and muzzle sound depending on with/without BB and BB weight for that matter.

If this is not different, the main cause is usually that the rifle is not as airtight as it should be, for whatever reason.

If your piston goes klonk both with and without BB, it is not sealing or energizing (too heavy piston + too light BB or no pressure lock).

On the other end of the spectrum, if you use a very light piston, combined with lifting 0.50, it will practically stop the piston on the air pressure.

If your piston weights 25-30gr, this is too light probably. You can try adding "golfers lead tape" (every VSR builder should have this for fine tuning) on the piston. A few wraps will get it to 40-45gr, which should be enough to notice an immediate improvement.

Can you say what piston, barrel, bucking and spacer you use currently?

Also you should use at least 1 sorbo pad for good measure.

You can also try different cylinder head with bigger bore ID.
 
if you use a very light piston, combined with lifting 0.50, it will practically stop the piston on the air pressure.
This may happen if you had a very weak spring and/or the nub was too far down but if you are shooting 0.5gm bb's, then you would use a pretty good sized spring.
With a weak spring and the nub too far down, then even a heavier piston can have the same issue because the piston would struggle to get up momentum since the bb is not being released. Pressure builds up in front of the piston and eventually it cannot move. You would be better off in this instance to use a lighter piston as it may give more of the pressure spike in its initial movement that is needed to get the bb past the nub.
 
csakip, are you still using the stock barrel and spring? If you're going to downgrade the spring, I'd suggest getting a new barrel first, a tighter one probably. That would fix your undervolumisation (is that even a word?)
 
i have an ssg24 with short barrel,m180 spring, and if my calculations are right i currently have a 3.03:1 ratio. ive been chronoed on site for 555 fps with 0.2bbs
i want to run with 0.48/0.49bbs, is this setup ideal for this weight? or should i increase the fps? i also have an m190 spring and 3 fps adjuster rings in my possession(in my country 600fps is the legal limit)
 
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