M14, hop issue- fps drop/bucking swelling?

[Grounded_Pilot]

Well, I have a brand new CYMA M14. And she is lovely.

After it being ordered from abroad I am not hugely keen on returning it either...

The gun fires excellently, it seems, for the first half hour of games. After about 25mins in, using semi auto, there is a noticeable failure rate of shots. (i.e. one in x amount of shots dip low)
5 minutes later, the whole thing jams up, barrel gets blocked on occasion, and any bbs that do fire come out around 150fps and drop about 5m in front of me.

I am rather well versed in AEG repairs, but after stripping down, examining the hop unit/barrel/hop bucking/nub/air nozzle, all seems FINE.

• The Hop unit is not damaged,
• The air nozzle is not cracked,
• The barrel is clean (and cleaned anyway to make sure)
• The hop bucking/rubber is clean, blemish free and with no signs of damage/tearing. Was a little too much grease first time it was stripped.
• The Nub is intact and a correct size.
• I have tried a varied selection of 0.2g & 0.25g BBs... of all sorts of manufacturers... with the exact same results.
• Also, I have replaced the original hop rubber with a Madbull Red Accelerator... with no luck...
• Hop is turned as far off as humanly possible, the screw can't physically move further out due to the body of the gun stopping it.

If anyone has an idea, or has been in the same boat as me... please get in touch. I am at my wit's end...!! Being a site techie/owner, it really kicks my ego into touch if I can't fix my own rifle!!
My only remaining idea is:

• Replace hop unit entirely and hope for the best.

The worst thing is, once the gun "cools down" it fires without a hitch... so will take a couple of hundred rounds before you work out if the issue is fixed, or not.

[mr lean 81]

Re: M14, hop issue- fps drop/bucking swelling?

Try another rubber, I have great range and consistency with guarder clear and prometheus barrel combo in my cyma m14.
Madbull are a tad thick so can cause issues.

[Grounded_Pilot]

Re: M14, hop issue- fps drop/bucking swelling?

I have actually gotten in touch with the company and they have been kind enough to arrange free postage return! (How lovely of them!)

So the gun is no longer in my hands but nevertheless it baffles me! It must have been the hop unit damaged because it just applied too much hop all the time... just a lemon I guess. Only ever heard good things about CYMA M14's!