G & P M4 Spec Ops

[Suzuki Yamamoto]

I've had a G & P M4 Spec Ops for a while now and the FPS when I first got it was around the 320 mark. I skirmished with it a few weeks ago after a lay off of around 18 months and the FPS has dropped to around the 285 mark. It now also seems to misfire on Semi Auto every so often and I have to put it into Full Auto and give it a quick burst to get it going again.

 

I'm no AEG expert so i'm seeking some advice from the forum experts in here as to what could be causing the issue.

 

I am also interested on what upgrade's could benefit this gun in the long term.

 

Your replies are greatly appreciated!!

[bigshep]

Might be something as simple as your battery is knackered after month lay off. It can't provide enough uumph to drive the motor enough to cycle the gearbox fully. Can you borrow a known good battery and try that?

[Suzuki Yamamoto]

Might be something as simple as your battery is knackered after month lay off. It can't provide enough uumph to drive the motor enough to cycle the gearbox fully. Can you borrow a known good battery and try that?

 

What battery would you recommend? Was thinking of getting a Lipo for this gun. Not sure on what voltage to go for though.

[bigshep]

to be honest I don't use lipo so can't comment, however I would just replace the one you have from somewhere like the component shop

 

http://www.component-shop.co.uk/

 

Should only cost £10-20 to do so and you get a known good battery.

[Liam Porter]

What battery are you currently using?

[Suzuki Yamamoto]

What battery are you currently using?

 

 

Hi Liam,

 

I'm just using the battery it came with. It's a 3 piece candle stick battery that fits into the crane stock of the gun.

[Liam Porter]

I hate though batteries , I used to have one and every time I adjusted the stock, the wires would get caught and eventually snapped.

 

 

Anyway, what voltage and mAh is it?

[Suzuki Yamamoto]

I hate though batteries , I used to have one and every time I adjusted the stock, the wires would get caught and eventually snapped.

 

 

Anyway, what voltage and mAh is it?

 

 

I have'nt got the foggiest i'm afraid. It came in the box when I got the gun.....I do agree about the battery being in the way inside the stock. Thats why I was considering a lipo because of it's size.

[Suzuki Yamamoto]

I hate though batteries , I used to have one and every time I adjusted the stock, the wires would get caught and eventually snapped.

 

 

Anyway, what voltage and mAh is it?

 

 

Just looked it up and it's an 8.4v and MAH 2200.

[Liam Porter]

I was gonna say if it's a low mAh then that may be the problem with the locking in semi. My G&P M16 won't run on low (1600) mAh batteries as it just locks up.

[RR01]

Your FPS drop off is probably down to a dried out piston seal. If you can take the upper receiver off, try putting a few drops of silicon cylinder lub down the nozzle, then leave the gearbox standing upright for an hour to let the oil penetrate the piston head. Once that's done, dry fire it a few times to spread the oil on to the cylinder wall, then give it a couple of short full auto bursts to get rid of the excess. Then put it back together and fire of about 30-50 rounds, then chrono it. That hopefully should get your FPS back up, but if not, then you may need to strip the gearbox as it could be that you left it after the the original lay-off with the piston under a bit of tension, in which case the spring will have settled and may need replacing. The gearbox could also need a strip, clean and re-lub.

 

As regards the battery, if you left it uncharged for 18 months then it could easily have lost the ability to retain a full charge. If it was discharged when you came to use it again it would probably have dropped well below the normal minimum of 1.2V per cell. You could try repeated charge and discharge cycles (a discharger would help there) as about 3 or 4 cycles might get it back somewhere near normal, but NihM cells can degrade well below a useful level in 18 months.

 

Oh, and just in case you're not aware, the duff battery won't have any effect on FPS, just on RPS (rounds per second).

[Suzuki Yamamoto]

Your FPS drop off is probably down to a dried out piston seal. If you can take the upper receiver off, try putting a few drops of silicon cylinder lub down the nozzle, then leave the gearbox standing upright for an hour to let the oil penetrate the piston head. Once that's done, dry fire it a few times to spread the oil on to the cylinder wall, then give it a couple of short full auto bursts to get rid of the excess. Then put it back together and fire of about 30-50 rounds, then chrono it. That hopefully should get your FPS back up, but if not, then you may need to strip the gearbox as it could be that you left it after the the original lay-off with the piston under a bit of tension, in which case the spring will have settled and may need replacing. The gearbox could also need a strip, clean and re-lub.

 

As regards the battery, if you left it uncharged for 18 months then it could easily have lost the ability to retain a full charge. If it was discharged when you came to use it again it would probably have dropped well below the normal minimum of 1.2V per cell. You could try repeated charge and discharge cycles (a discharger would help there) as about 3 or 4 cycles might get it back somewhere near normal, but NihM cells can degrade well below a useful level in 18 months.

 

Oh, and just in case you're not aware, the duff battery won't have any effect on FPS, just on RPS (rounds per second).

 

Thanks RR01. Although I'm not very good at taking these guns apart and could'nt really tell what all the components are. WIll probably pop it into my local store and get one of the techs to have a look at it. I might, if time allows me, try and pop it open and try the lube trick that you suggested.

 

Thanks again for the advice, it's really appreciated!!