Some easy simple Airsoft Maths that I think work

[Sitting Duck]

If anybody is actually interested.......

Just done some quick rough tests on 2 guns that I think are over volume'd

 

1st gun is deffo way over volume'd

it should be hitting about 300+ but is hitting 240 !!!

(this increases a fair bit to 280 with a longer barrel but this is too long so under volume'd)

 

2nd gun I strongly suspect the port is marginally incorrect - hitting nearly 300 but likely to hit 345

 

Also I think though over volume may push out heavier bb's better perhaps on gas guns/pistols

this does not quite seem to be the case on AEG's - I'll explain......

 

1st gun - seriously over volumed - barrel needs to be about 120mm longer I reckon by my maths

(deffo seen higher fps on longer - but too long barrels so a little under expected fps)

240fps on 0.20's average

 

So I thought I might see a slight increase or same on heavier bb's rather than usual drop

(sounds reasonable if ya pushing out too much air for 0.2 but might be good for .25 or .30's)

 

NOPE both guns did not show any close performance at all on using .25's or .30's

 

240 on 0.20's

215 on 0.25's

190 on 0.30's

 

aprox 25 fps drop each 0.05g increase

 

2nd gun - I suspect needs a barrel maybe about 80mm longer for the current port position

(haven't tried slightly longer barrels but I have a gut feeling the port is a bit out)

 

300 on 0.20's

270 on 0.25's

240 on 0.30's

 

aprox 30fps drop for each 0.05g increase - but starting figure is higher if that means owt

 

So the above crap kind of blows the idea that an over volume'd aeg will push out heavier bb's

much much more effectively and maybe close to 0.20 performance......

(well it might if you whack in a heavier M120 spring on first gun but not tried that and probably won't atm)

 

Also by studying the output figures it might come to light on the performance lost factor

 

THIS IS JUST A ROUGH AS OLD BOOTS FIRST GUESS THOUGH......

 

Gun 1 has a barrel aprox 120mm too short I strongly reckon - take half of that 120 figure = 60

add 60 to 240 then that would equate to about the right amount expected 300fps

sounds a lot but this is well n over volumed and the seals are or was very good

(it is a CM FireHawk with a 120mm barrel and a port for about 250mm)

 

Gun 2 has a barrel I think of about 80mm too short - take 50% of that 80 = 40

add 40 to 300 and I really think it should been hitting about 340+ fps

(crappy SRC with a 275mm barrel and a port I cut on full cylinder that I reckon was more for a 363 aprox)

I haven't tested this second gun a lot or with any other different barrel lengths

 

But there ya go - 2 guns over volume'd and serious drop in performance from it

(rough estimate though as to performance lost but I do think hop/tappet/nozzle is sealing good before you think its that)

 

Also - Ithink my calculation of 12mm might be a litle too low

 

I think the more accurate figure is about 15mm to 16mm as the O-ring on piston can sit quite far back on some

 

Suffice to say correcting the AOE can vary - usually it is about 4mm-ish but recently had a box that needed 7mm - no $hitting 7 bloomin mm ffs !!!

(in the end I put a 5mm spacer behind piston head - checking central alingment to piston & a thin sorbo/washer on cylinder head)

 

So yeah - ignore the 12mm & go with say 15mm off the port measurement chaps - my bad