How many fps would you gain by increasing barrel length by 4cm

[steverebo]

As stated above I want to increase my fps a bit I'm using a 300mm zci 6.02 barrel how much fps would I gain by increasing the barrel length to 340mm?

 

[Davegolf]

AEG, GBB or HPA?

As an average id say 15fps maybe

 

[steverebo]

AEG 

 

[Skara]

Hard to quantify.

Even two guns with the same exact parts will have different energy outputs.

Also depends on your cylinder/barrel volume ratio, generally a longer barrel will boost energy output but only until a certain point, after that you'll experience a decrease.

What's your gun's spec?

 

[Cannonfodder]

As I understand it for aegs barrel length has bugger all, if any, affect on fps. 

 

[Guest]

Airsoft Engenuity did a study on loads of different spec AEG’s and on all of them FPS tailed off to essentially zero gain after about a total length of 260mm.

All different bores, hops, gearbox specs etc etc, they all tailed off around 260

 

[Davegolf]

Thats not really true, there are so many variables.

If you were sticking purely to the same spring, cylinder type, bb weight, barrel ratio etc etc etc then yes.

Most stock AEGS are well over volumed on 0.2s, (for those not aware - this essentially means the BB has left the barrel but air is still coming out) so if you increase the barrel length you will impart more energy and therefor speed into given BB.

This is exploited most by GBB as they 'self-volume' thanks to the floating valve.

@steverebo i think you will pick up 15 fps (+/-5)

 

[Guest]

Thats not really true, there are so many variables.

If you were sticking purely to the same spring, cylinder type, bb weight, barrel ratio etc etc etc then yes.

That’s exactly what I said.

Whatever your fps in whatever AEG you have, any length over about 260mm will make little to no difference. Apparently. I didn’t do the testing

 

[Adolf Hamster]

As I understand it for aegs barrel length has bugger all, if any, affect on fps. 

yep, they're constant energy systems as opposed to constant force systems (ie your gbb's/hpa's) so outside the extremes it won't make significant difference.

that's not to say it won't change, but that's typically when you have a system with suboptimal sealing that gets fixed incidental to the actual swapping of barrels like re-seating/replacing the hop bucking or reassembling the unit into the gun. ofc how much those gains may be will be hard to quantify for any given gun.

 

[Davegolf]

@rocketdogbert i suppose you did, yes.

Using my recent AK as an example, actually exact same lengths as OP - had a 300 - fitted a 340, picked up 10 fps, backed up by more joule creep / less energy loss with heavier ammo.

Same barrel make and bore, same bucking, hop unit, nozzle, everthing.

OP been pretty shy on details so whatever, its pot luck really.

 

[Sneaky]

There will not be much in it. Should get it chrono’ed, then change the barrel straight away, then retest and you will have your answer. 

 

[Davegolf]

No shit ?

 

[JimFromHorsham]

You could always cut it down if it’s too much ??‍

 

[Rogerborg]

If you were sticking purely to the same spring, cylinder type, bb weight, barrel ratio etc etc etc then yes.

Like OP seems to be planning?

I'm going to go with zero, or "airsoft zero" (i.e. an imaginary boost), unless 1) he's running a full cylinder, or 2) he changes some other variable.

 

[Dan Robinson]

You could always cut it down if it’s too much ??‍

By as much as 4cm ?

 

[steverebo]

Cheers guys purely from reading all the comments I'm going to grab the 340mm even if I don't end up sticking with it as they are only cheap and see if I gain anything or nothing and feed back my results.

I did skimp on the details it's an 416d with 3/4 cylinder short stroked by 4 teeth (2 pickup 2 release) warhead motor stock nozzle which has an oring and seals perfectly, zci hop unit and maple leaf Mr hop 60.

 

[Rogerborg]

3/4 cylinder short stroked by 4 teeth (2 pickup 2 release)

I'd be surprised if you're not already under-volumed for 300mm - but I'm often surprised by what passes for physics in airsoft.  If you don't get a boost, or even see a drop, you could... uh... stick some teeth... no, wait, let me think about this a bit more. ?

I'm invested in this process now: do you know what spring is in there?  And what muzzle energy you're getting just now (and on what BB weights)?

 

[steverebo]

I cannot remember the spring but its shooting 280fps with .28 bb's on average with a variance of around 5fps 

I would like to get it up to around 290 without having to mess with my spring as it's a right pain getting to it

 

[Cr0-Magnon]

shooting 280fps with .28 bb's on average with a variance of around 5fps 

So why worry? The very max on a 0.28g is 295fps and you wouldn't even want to go that far due to variance in site chrono's.

 

[Rogerborg]

The very max on a 0.28g is 295fps and you wouldn't even want to go that far due to variance in site chrono's.

Or playing at a dinosaur site that chonos in 0.2g, or says "hop off, mate, hop off".

For example, my G36C also chronos bang on 1J (OK, "280fps") shooting and hopped for 0.28g.

Put in 0.2g and hop for that - or dial the hop off - and it leaps up to... well... not quite Section 5, but enough to make CQB sites shriek in horror.  Luckily it has an adjustable spring guide / pre-tensioner to cool it down.

If you're absolutely sure about the sites and testing policy, then chasing 1.13J is reasonable. I'm fine keeping my AEGs down at 1J with 0.28g though.