G&G Mis-Feed After Spring Change

[Miki01]

Hey guys, I recently picked up a G&G RK74 CQB from Toronto Airsoft. Before playing my first game I had the gun chrono'd and it was shooting a little hot at 395fps. I took the gun home and threw a spring I spare spring I had and dropped it to 340fps. A little lower than I'd like, but at least I could still play. Original spring is an irregular-pitch spring, current one is a regular linear spring.

I noticed that after the spring change, anytime I use a completely full magazine (4x G&G RK74 mags), the gun would mis-feed. Sometimes it a BB shoots at maybe 0.5fps and land in front of me, sometimes nothing, sometimes one at proper fps.

The gun itself feeds fine when the mags are filled 10-15rnds before full.

I took the gun apart again tonight to double check my hop up, clean the barrel, as well as check to make sure I had the nozzle grooves properly mounted to the tappet plate grooves and everything is good to go. In terms of BBs, I currently run 0.28g Krytac, but I did try 0.25g Krytac and 0.25g Elite Force with the exact same results. Hop-up in the full on or full off position doesn't make a difference. I even tried playing with the mag seating considering this gun has a rubber plate that centers the mags and prevents it from wobbling, but no difference.

I'm fairly new to playing gun doctor, but I don't mind it as I do come from a mechanical background and have rebuilt/modified a V3 gearbox and an ICS split gearbox in the past, so I have no problems digging in and getting dirty.

Any ideas would be greatly appreciated.

Thanks

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[Styrak]

http://www.airsoftcanada.com/showthread.php?t=169828

[Miki01]

Originally Posted by Styrak

http://www.airsoftcanada.com/showthread.php?t=169828

Hi Styrak, I'll certainly look into that, thanks.

Any idea why something as simple as a spring change would cause something like this? Gun has less than 1500rds through it.

Also, do you think throwing in an SHS metal air nozzle would be beneficial?

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[Styrak]

Only happened after the spring change? Maybe you didn't shoot it enough to notice before the change? Not sure.

[Miki01]

Originally Posted by Styrak

Only happened after the spring change? Maybe you didn't shoot it enough to notice before the change? Not sure.

I shot four or five mags (115rd/each iirc) after the spring change. The rest of the rounds were fired with full mags on the factory spring.

I'm going to try a stiffer tappet spring and an SHS aluminum nozzle for now to see if that aleviates it.

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[Miki01]

So I've swapped out to an SHS aluminum nozzle with O-ring as well as swapped out my tappet plate spring (same one as used in the linked thread above).

Absolutely no difference in performance.

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[RainyEyes]

Sand down the lips on the g&g hop up rubber or swap it with a lonex one.

One of the local retailers got a batch of off-spec/defective g&g rubbers. See if that does anything. Mine had the same problem.

[Miki01]

Originally Posted by RainyEyes

Sand down the lips on the g&g hop up rubber or swap it with a lonex one.

One of the local retailers got a batch of off-spec/defective g&g rubbers. See if that does anything. Mine had the same problem.

I assume the lips aren't supposed to be visible when looking down the feed hole?

It's weird trying to figure out what caused this. It was perfectly fine going through all 4 mags before I swapped to a lower FPS spring. I didn't touch anything else on the gun.

When I went to Seige last week, guy who chrono'd my gun just used a random MP5 mag and shoved it in the mag feed and fire from there. You think an aftermarket mag that sits differently could force itself onto the nozzle and in turn bend the cylinder head nozzle?

The cylinder head is made of brass, so I may upgrade it later on.

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[RainyEyes]

Sorry sand down the thickness, not the length. If the hop up lips are too tight then it might be providing too much resistance to the nozzle so that it may cause misfeeding.

The lips being visible is irrelevant because the manufacturer will offset the rubber length with the nozzle length.