Ian_Gere
Retired Moderator
- Apr 1, 2012
- 6,417
- 2,050
Well, the CM.039C is a TM clone, so inherent problems you will face are that the barrel base assembly which also holds the rear of the gas tube, is not as hollow as some other makes which means that it can be a bit of a struggle to get your battery connector and wire stuffed into that space, but you can have to if you're using a folding stock, or in your case, unless you mod the trunnion to allow for a battery inside the buffer tube, because an 8.4V NiMh stick battery fills that top space under the dust cover exactly.
You can get Turnigy Nano-Tech LiPo's of 7.4V or 11.1V in that space with a little wiggle room however, but it is a real struggle to find enough space for anything but the smallest MOSFET without pretty major dremmel-mods to allow the FET board to sit somewhere inside the front handguards. Removing the small Tamiya connectors in favour of Deans connectors gives a few valuable cubic millimetres of extra space, as well as conducting electricity better...
The shimming on CYMA's is pretty rudimentary, in fact the gearbox works so well because the tolerances of everything are slacker than the original from which they are cloned - basically their solution to the problem of putting a more powerful spring in than the TM and still wanting great ROF is to just throw more power at it and consequently the GB is pretty noisy compared to many others.
Another potential problem is the air seal nozzle, which is very short compared to other AK designs so is a bit of a pig to replace with aluminium, and the original is prone to tiny cracks in its clear polycarbonate. They're not exactly known for a good air seal even when brand new, even though their stock hop rubber is very good at spinning up BB's and centring them in the barrel for better accuracy. Again, their solution is to use more power, ie more air coming faster out of the cylinder - I don't think anyone in the west knows for sure what weight of spring they use as standard, but my guess is that it's more than an M120 but not as high as an M130 but fortunately, for nothing more than the cost of the spring you want in the gun, taiwangun.com (and many other retailers) will supply it to you with the spring of your choice already fitted - a M110 gives you about 360+/-5 an M100 about 330+/-5 FPS - the way forward is an Element M105 which gives you about 345+/-5, but taiwangun don't sell that spring
The easiest way to get more FPS out of a sub 350FPS CYMA AK is to change the air seal nozzle for a black POM one - I forget right now, but I think Dream Army do one - iirc the replacement needs to be 19.5mm long, which is 0.18mm longer than the stock one and, while the gears and shell are usually liberally coated with earwax looking grease, inside the cylinder isn't. A good smear of Guarder Teflon grease on the O-ring does wonders, but don't worry about the piston head, cylinder head, or piston unless you're prepared to completely tune up the GB - hopefully the piston head of the .039 series retains the tiny acetate washer from the .028 series between the piston and head, which acts almost as a 2nd O-ring.
*massive inhalation*
Hooooooooooooooooooooowever...
I'm 80% sure that the Model B (also called Beta or Omega on some sites) replacement trunnion UTJ referred to above is intended to fit onto any AK-74 with a left folding stock. The problem is that, as Ed points out, we dunno how the tube actually attaches to that type of fixed or folding trunnion. I have to say that getting the pin out of the hinge to swap to that folding trunnion may not be anything like easy - for a fact I know it would be a very annoying job on my ICS AKS-74U. CKinnerly has yanked up an AK before so maybe he knows, or Finius...?
You can get Turnigy Nano-Tech LiPo's of 7.4V or 11.1V in that space with a little wiggle room however, but it is a real struggle to find enough space for anything but the smallest MOSFET without pretty major dremmel-mods to allow the FET board to sit somewhere inside the front handguards. Removing the small Tamiya connectors in favour of Deans connectors gives a few valuable cubic millimetres of extra space, as well as conducting electricity better...
The shimming on CYMA's is pretty rudimentary, in fact the gearbox works so well because the tolerances of everything are slacker than the original from which they are cloned - basically their solution to the problem of putting a more powerful spring in than the TM and still wanting great ROF is to just throw more power at it and consequently the GB is pretty noisy compared to many others.
Another potential problem is the air seal nozzle, which is very short compared to other AK designs so is a bit of a pig to replace with aluminium, and the original is prone to tiny cracks in its clear polycarbonate. They're not exactly known for a good air seal even when brand new, even though their stock hop rubber is very good at spinning up BB's and centring them in the barrel for better accuracy. Again, their solution is to use more power, ie more air coming faster out of the cylinder - I don't think anyone in the west knows for sure what weight of spring they use as standard, but my guess is that it's more than an M120 but not as high as an M130 but fortunately, for nothing more than the cost of the spring you want in the gun, taiwangun.com (and many other retailers) will supply it to you with the spring of your choice already fitted - a M110 gives you about 360+/-5 an M100 about 330+/-5 FPS - the way forward is an Element M105 which gives you about 345+/-5, but taiwangun don't sell that spring
The easiest way to get more FPS out of a sub 350FPS CYMA AK is to change the air seal nozzle for a black POM one - I forget right now, but I think Dream Army do one - iirc the replacement needs to be 19.5mm long, which is 0.18mm longer than the stock one and, while the gears and shell are usually liberally coated with earwax looking grease, inside the cylinder isn't. A good smear of Guarder Teflon grease on the O-ring does wonders, but don't worry about the piston head, cylinder head, or piston unless you're prepared to completely tune up the GB - hopefully the piston head of the .039 series retains the tiny acetate washer from the .028 series between the piston and head, which acts almost as a 2nd O-ring.
*massive inhalation*
Hooooooooooooooooooooowever...
I'm 80% sure that the Model B (also called Beta or Omega on some sites) replacement trunnion UTJ referred to above is intended to fit onto any AK-74 with a left folding stock. The problem is that, as Ed points out, we dunno how the tube actually attaches to that type of fixed or folding trunnion. I have to say that getting the pin out of the hinge to swap to that folding trunnion may not be anything like easy - for a fact I know it would be a very annoying job on my ICS AKS-74U. CKinnerly has yanked up an AK before so maybe he knows, or Finius...?
)
