Barrel Length Vs FPS

[doa88]

Hi everyone

 sincere apologies if this is a repeated topic. I have tried to search it but haven’t found any good results

 I recently swapped my barrel in my AEG rifle from a circa 250mm barrel to a circa 125mm barrel. Before the swap, the FPS was @ around 320. Today the gun Chronoed @ 279. I used identical bucking and hop mechanism and the gun fired and fed fine all day so I don’t think there was an issue there.

question: Is this drop in FPS normal when you reduce the barrel length, and is the fix simply ordering a heavier spring?

thank you

 

[Iceni]

Yup perfectly normal.

Longer barrels are always faster.

And yes a slightly heavier spring is the normal way to counter this. It's why airsoft spring ratings are more like guidelines. Barrel length of the gun, Gearbox compression, Airseal ect all change the FPS.

 

[EDcase]

Yeah,  250mm is already quite short and you've halved it to nearly pistol length.   There just isn't time for the air pressure to accelerate the BB before its out so you have to increase the pressure with a heavier spring.

Heavier spring will of course put more strain on gearbox parts...

 

[Hatchet]

"Longer barrels are always faster"? Surely the cylinder is a factor here? If you're running an optimally volumed cylinder for your barrel, sticking a longer one on isn't going to magically make it faster. (Although, yes, if you're not it can).

If you're moving to a barrel that short I'd expect you'd need to swap from a 3/4 cylinder to a 1/2 ported cylinder, depending on what you had in there before, what weight of ammo you're using, etc.

 

[Druid799]

Yeah,  250mm is already quite short and you've halved it to nearly pistol length.   There just isn't time for the air pressure to accelerate the BB before its out so you have to increase the pressure with a heavier spring.

Heavier spring will of course put more strain on gearbox parts...

Click to shrink...

Which will then lead on to gearbox upgrades , which then leads on to a motor upgrade , which then leads on to hop upgrades , which THEN traps you in never ending hell of ‘triggers broom’ ! ??

 

[doa88]

Thanks for your help guys.