AK5c Low fps

SixthFall · February 5th, 2014, 13:49

I have been having no end of issues with my ak5c. Let me give you some background. There is a 4mm bolt that screws the stock into the back of the gearbox, but when you tighten the bolt, it pulls on the gearbox, causing a misalignment between the airnozzle and hopup while the nozzle is in battery. I have tried to shim the gearbox forwards to counteract this, and the gun feeds reliably, but i am getting sub 300 fps, sometimes as low as sub 100 when it should be shooting about 420 (upgraded compression parts and cylinder) I have no idea how to shim either the hopup, or the gearbox, so the nozzle contacts the bucking and forms a seal, it has a slight upward angle at the tip, which is the problem (due to misalignment of the gearbox as stated above i think). And i was hoping maybe you folks had a fresh perspective for me? I am about ready to throw the damn thing off a cliff here.:banghead::banghead:

HKGhost · February 5th, 2014, 14:57

The low FPS could also be caused by the gearbox being pulled back a bit, and causing a gap between the nozzle and bucking. Try using metal washers to shim the gearbox forward.

SixthFall · February 5th, 2014, 16:08

Done, didn't help. I removed the hop up spring and stuck an o ring in its place, seems to be working now, I'll run some rounds through it and see

danhay · February 6th, 2014, 17:07

Try putting a shim made out of a chunk out of an old credit card between the rear of the gearbox and that metal sleeve that fits around the stock screw (which acts to hold the fake bolt and recoil guide rod in place). This shim will push the gearbox a little down and forward thus ensuring that when the nozzle returns to battery it will form a good seal with the hopup rubber.

A friend just performed that very modification and found that it cleaned up the velocity issues he was experiencing. Both he and I were experiencing very low velocity (100-150 fps) on the first 10 or so rounds out of a full midcap. He discovered that an already slightly mis-aligned nozzle would be pushed out of position by the pressure of a full midcap just enough that poor air-seal would result.

I'll be performing that modification myself in the near future. I will report back with the results.

Ryland, if you're reading this please chime in!

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February 5th, 2014, 13:49	#1
SixthFall Trader rating Join Date: May 2012	AK5c Low fps I have been having no end of issues with my ak5c. Let me give you some background. There is a 4mm bolt that screws the stock into the back of the gearbox, but when you tighten the bolt, it pulls on the gearbox, causing a misalignment between the airnozzle and hopup while the nozzle is in battery. I have tried to shim the gearbox forwards to counteract this, and the gun feeds reliably, but i am getting sub 300 fps, sometimes as low as sub 100 when it should be shooting about 420 (upgraded compression parts and cylinder) I have no idea how to shim either the hopup, or the gearbox, so the nozzle contacts the bucking and forms a seal, it has a slight upward angle at the tip, which is the problem (due to misalignment of the gearbox as stated above i think). And i was hoping maybe you folks had a fresh perspective for me? I am about ready to throw the damn thing off a cliff here.:banghead::banghead:

February 5th, 2014, 14:57	#2
HKGhost Trader rating Join Date: Nov 2009 Location: Mississauga, ON	The low FPS could also be caused by the gearbox being pulled back a bit, and causing a gap between the nozzle and bucking. Try using metal washers to shim the gearbox forward. __________________ Please email me as I'm not on ASC too often. Custom Build \| Upgrades \| Repairs \| Maintenance Contact: ghostgunwork@gmail.com / Private Message

February 5th, 2014, 16:08	#3
SixthFall Trader rating Join Date: May 2012	Done, didn't help. I removed the hop up spring and stuck an o ring in its place, seems to be working now, I'll run some rounds through it and see

February 6th, 2014, 17:07	#4
danhay Trader rating Join Date: Jun 2011 Location: Calgary, AB	Try putting a shim made out of a chunk out of an old credit card between the rear of the gearbox and that metal sleeve that fits around the stock screw (which acts to hold the fake bolt and recoil guide rod in place). This shim will push the gearbox a little down and forward thus ensuring that when the nozzle returns to battery it will form a good seal with the hopup rubber. A friend just performed that very modification and found that it cleaned up the velocity issues he was experiencing. Both he and I were experiencing very low velocity (100-150 fps) on the first 10 or so rounds out of a full midcap. He discovered that an already slightly mis-aligned nozzle would be pushed out of position by the pressure of a full midcap just enough that poor air-seal would result. I'll be performing that modification myself in the near future. I will report back with the results. Ryland, if you're reading this please chime in!

AK5c Low fps

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