Brand new gearbox and spring, shitty fps

[Baroc]

hey guys, I have a kraken ak (which is pretty much all aftermarket). recently it has started shooting around 300 fps, traditionally it had been around 400 and that's my goal. now I installed a new metal hop up, a new nub, a brand new whole king arms gearbox and a new high speed motor. the gearbox came with a m120 spring. my gun still chrono's around 300 fps... I don't know what the problem could be anymore... any ideas?

[Hectic]

Is the nozzle and hopup sealing well? Seems like its prolly an airseal issue the hop to nozzle connection is prolly yer best bet as the culprit

[coach]

You have changed too many variables at once to zero in on the actual problem. You have essentially built a low end kraken from the ground up. It could be that the receiver is not straight and the KA gear box doesn't line up to your hopup not fitting right or even the rubber not seated right.

[Baroc]

I now think I know the problem. it appears that my brand new king arms gearbox comes with an air nozzle that is too short to properly aware into the hop up chamber.either the nozzle is too short, or out does not fully extend when it shoots (it appears more sunken than my original gearbox). any ideas?

[Rusty Lugnuts]

different length nozzles are unlikely, To compare them you have to ensure both boxes are at the same point in their cycle, easiest way to do that would be release the anti reversal latch thereby allowing the spring to push the piston all the way forward. To release the anti reversal latch on some mechboxes there is a handy hole on others you can hook it thru the motor hole.

[MaciekA]

Originally Posted by Baroc

I now think I know the problem. it appears that my brand new king arms gearbox comes with an air nozzle that is too short to properly aware into the hop up chamber.either the nozzle is too short, or out does not fully extend when it shoots (it appears more sunken than my original gearbox). any ideas?

You should only judge the position of the seal if you have released the anti-reversal latch so that the gears relax and the tappet plate can move fully forward. It's completely normal for the nozzle to be in a wide range of positions after taking shots both in full auto and semi-auto. It's pretty hard to guarantee it will be in the full forward position.

Grab a long hooked metal tool (I like to use dental / surgical tools for this sort of thing), stick it in your gearbox when you've removed the motor, and release the ARL. Then check nozzle position by jamming your hopup chamber against your gearbox.

Also check you haven't forgotten the hopup tension spring.

[ThunderCactus]

I thought the kraken mechboxes were longer than normal?

[Baroc]

@ Thunder: The mechboxes are the exact same shape and size in every aspect.

I've got a game coming up in 7 days, I rather not open the gearbox for now. It's BRAND new I've never opened it before. I just find it's weird the Air Nozzle doesn't extend all the way on a new piece of hardware.

Anyways, I'll crack it open after the game to see what's what.

[Stealth]

Brand new gearbox doesn't count for much when the tolerances aren't right.

I just opened up an King Arms M4 mechbox and the tappet plate doesn't allow the nozzle to extend all the way forwards - causing a massive air leak.. This is just an example.

[lurkingknight]

Originally Posted by Rusty Lugnuts

different length nozzles are unlikely...

I have a modify p90, guarder p90, CA p90 and lonex p90 nozzles all on my work bench and a set of digital calipers that will tell you otherwise.

Also a modify/lonex/CA g36 nozzles that are also of varying lengths. Fractions of a mm can make a difference.

[Rusty Lugnuts]

Originally Posted by lurkingknight

I have a modify p90, guarder p90, CA p90 and lonex p90 nozzles all on my work bench and a set of digital calipers that will tell you otherwise.

Also a modify/lonex/CA g36 nozzles that are also of varying lengths. Fractions of a mm can make a difference.

Digital calipers is cheating he said appears

[lurkingknight]

you can still visually check them if you rest them on a flat surface. You'll also notice the channel where the tappet locks into is also cut more forward or rearwards depending on brand, and even batch sometimes (shs 14th tooth piston anyone?) if you look closely enough. just a tiny difference like that can move the tip of from nozzle to nozzle to cause a leak or misfeed when you combine it with any other number of manufacturing factors in airsoft. I make it standard practice to measure every single part that comes out of a gun now.. from gear tooth thickness to bore diameter of nozzles.

I'm not talking thousandths of a mm here, I'm talking hundredths and sometimes even tenths of a mm difference.

[ThunderCactus]

.010 inch will make a difference, I've made a few +10 and +20 thou nozzles before
But yeah, tappet plates man. The guarder ones are angled back for more reliable feeding, but pull the nozzle back from the hopup, for example

[Rusty Lugnuts]

In this particular case the OP was looking at two mechboxes and saying the nozzle looked longer on one, I contend that it was more likely the mechboxes were at different stages of the cycle, The noozles weren't out and standing on a flat surface. I'm aware that nozzles come in very slight difference in lengths. I was just going for the most likely explanation. Geez!

[ThunderCactus]

lol well if it makes you feel any better I measured 3 systema, 2 guarder, and 5 G&P nozzles, there was a .005" difference at most between them all, and the brands were within .003" of eachother. They're pretty damn consistent!

They could be different lengths if one had a guarder tappet and the other a systema (for examples), but I think the guarder plate only takes .02" or so off the stroke, could be wrong