Need help whit my KWA M4 TAC
 

Got my KWA M4 this summer. New out of the book it was shooting 435fps.
So for my first game I used a velocity reduction adaptor. So I got an ms100 spring and it shoots at 320fps. Then bought a bore up kit from Modify, with a m120 spring. Now it shoots at below 300fps. Plus the MechBox cracked….
1 What MechBox should I buy?
2 Why is the gun shooting so low?
3 Do I need a bigger spring or what??????

Sounds like an air seal issue perhaps. I don't have enough experience with bore up kits though. But definitely an air seal issue imo. Don't use a heavier spring, solve that issue with the help of someone more educated.

As far as the mechbox goes, I would recommend a systemA mechbox. they are very good quality, all I use now.

If you're mechbox cracked that's probably why you have low FPS.

Thanks but the MechBox is not the problem. it's air flow in the piston.

Uh, then why are you asking questions you already know the answer to?

It could very well be the broken mechbox. Because mechboxes are not suppose to be BROKEN.

Where did your mechbox crack? Up front by the end of the cylinder? It'd be nice to get a pic...those KWA mechboxes are supposed to be reinforced and have more material up front than most reinforced mechboxes.

If you want to save yourself some headaches...
1. Buy a good quality mechbox (KA reinforced, Systema)
2. Use good quality bushings (modify make very nice ones that aren't expensive)
3. Don't use the aluminum piston head that came with the KWA
4. Unless you're running a really long inner barrel, there's no need for a bore-up kit
5. Unless you're KWA is different from most others...the hopup and nozzle are different than "normal" ones. There's a ridge that runs along the top of the nozzle that indexes into a notch in the hopup. If you're using a regular (i.e. plain, round) M4 nozzle (probably the bore up one that you installed) with the notched stock hopup unit...they probably aren't matching up well, resulting in an air loss. Doesn't take much to drop a lot of FPS.
6. The stock piston isn't bad...although I replaced a shattered one last week. Be sure to loctite the piston head onto it's screw.

A Modify M110 in your setup might put you over 400fps w/ 0.20g bbs...a Modify M100 will probably be in the 350-370fps range. But it depends on a lot of other factors.

Best of luck,

Tys

OH Well time to buy a new gun :]:D

shit,,,so many problems

im running stock kwa and its still going strong....all im dropping in is a sorbo pad and sorbo piston head. u should do that with ur next.k mechbox

Bore up kit on M100? You have mixed and mis-matched the parts.

m102404...sweet intel bro. Gotta remember this one (as a couple of the guys are starting to pick up the KWA M4S).
LOL, so thanks in advance.

SHA DO

Sha Do,

Solid rifles. Do them a favour and take out the solid aluminum piston head. I just repaired one that came loose...destroyed the piston and cylinder.

They do sound great and have a solid/loud "Thwack, thwack, thwack" sound...right up until they stop shooting. :D

Tys

Yeah, already told the guys that they'd have to also buy a silicone piston head and sorbo pad....

LOL,
SHA DO