M4 Low FPS Problem

Styrak · August 24th, 2008, 01:24

Hey there. I have a new Guarder reinforced mechbox with a normal ported cylinder, modify metal cylinder head, modify nozzle, element polycarb piston and bearing piston head.

I also am using a G&P metal hopup.

The problem is the FPS is hovering arounf 150-200 when it should be about 380-400.

Strange thing is, I had a different mechbox in there with the same barrel and hopup and it worked fine. The compression in the cylinder and nozzle is perfect.

I'm thinking it might be the nozzle-hopup connection? Not sure, but please help me if you have any ideas. I have another metal hopup here I'm gonna try to swap out.

Skladfin · August 24th, 2008, 01:25

what hop up rubber are you using?

mcguyver · August 24th, 2008, 01:29

Use the "test to see if air leaks out the hop-up feed nozzle" approach. Likely that's your issue. This can be attributed to improper length or profile of your gearbox nozzle. Or sometimes it's the mating between the hop-up and the mechbox.

CDN_Stalker · August 24th, 2008, 01:34

Could also be the ported piston head, I've had more issues with those int he past shooting low than I have with almost any other upgrade (ok, Madbull blue hop up rubbers consistantly give airleaks, so I stopped buying them). I DID have a good experience recently with using a wipe of silicon oil on the O-ring for a ported piston head, and it worked out great. All previous ones I'd put grease on, would test great for compression, but would end up sitting from shot to shot, 150-400fps, depending on the spring.

Styrak · August 24th, 2008, 01:38

Quote:

Originally Posted by Skladfin

what hop up rubber are you using?

Um. Not sure actually. I could try that out too but like I said it's the same barrel/hopup unit I used with the last mechbox. Didn't touch it.

Styrak · August 24th, 2008, 01:48

I have an idea. I have a sector clip installed because I'm using a 9.6v large battery. Maybe the nozzle is different dimensions and does not need the sector clip. Or it's just fucking up the cycle.

Changed to the other metal hopup and it's shooting about the same.

Styrak · August 24th, 2008, 02:06

Problem's fixed.

DO NOT install a sector clip with a modify airseal nozzle.

Shooting 375 now.

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August 24th, 2008, 01:24	#1
Styrak Trader rating Join Date: Jan 2007 Location: Saskatoon, SK	M4 Low FPS Problem Hey there. I have a new Guarder reinforced mechbox with a normal ported cylinder, modify metal cylinder head, modify nozzle, element polycarb piston and bearing piston head. I also am using a G&P metal hopup. The problem is the FPS is hovering arounf 150-200 when it should be about 380-400. Strange thing is, I had a different mechbox in there with the same barrel and hopup and it worked fine. The compression in the cylinder and nozzle is perfect. I'm thinking it might be the nozzle-hopup connection? Not sure, but please help me if you have any ideas. I have another metal hopup here I'm gonna try to swap out. __________________ Airsoft Sales and Repair/Upgrade Services

August 24th, 2008, 01:29	#3
mcguyver Trader rating Join Date: Aug 2005 Location: Northern Alberta	Use the "test to see if air leaks out the hop-up feed nozzle" approach. Likely that's your issue. This can be attributed to improper length or profile of your gearbox nozzle. Or sometimes it's the mating between the hop-up and the mechbox. __________________ Age verifier Northern Alberta Democracy is two wolves and a sheep discussing what's for dinner. Freedom is the wolves limping away while the sheep reloads. Never confuse freedom with democracy.

August 24th, 2008, 01:34	#4
CDN_Stalker Official ASC Bladesmith Trader rating Join Date: Jul 2003 Location: Ottawa, Ont.	Could also be the ported piston head, I've had more issues with those int he past shooting low than I have with almost any other upgrade (ok, Madbull blue hop up rubbers consistantly give airleaks, so I stopped buying them). I DID have a good experience recently with using a wipe of silicon oil on the O-ring for a ported piston head, and it worked out great. All previous ones I'd put grease on, would test great for compression, but would end up sitting from shot to shot, 150-400fps, depending on the spring. __________________ STKR Knives http://www.facebook.com/#!/pages/STK...17036668380871

August 24th, 2008, 01:25	#2
Skladfin Trader rating Join Date: Dec 2006 Location: Glace Bay, Nova Scotia	what hop up rubber are you using?

August 24th, 2008, 01:48	#6
Styrak Trader rating Join Date: Jan 2007 Location: Saskatoon, SK	I have an idea. I have a sector clip installed because I'm using a 9.6v large battery. Maybe the nozzle is different dimensions and does not need the sector clip. Or it's just fucking up the cycle. Changed to the other metal hopup and it's shooting about the same. __________________ Airsoft Sales and Repair/Upgrade Services

August 24th, 2008, 02:06	#7
Styrak Trader rating Join Date: Jan 2007 Location: Saskatoon, SK	Problem's fixed. DO NOT install a sector clip with a modify airseal nozzle. Shooting 375 now. __________________ Airsoft Sales and Repair/Upgrade Services

M4 Low FPS Problem

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