Dis assembly guide
http://airsoft.spells.dk/Guides.cshtml?Page=AKm249Para_Page1
(This guide is the AK but CA is the same way)
Yes a mosfet is GOOD on the 249!!! It also helps prevet the trigger problem.... and as you say then you can go lipo on it
Other than a mosfet and lipo ... Just basic stuf like: Check the shimming (Most of them are acturaly verry good). And just do some air sealing ....
One thing that you should concider is switching to a 3-4 metal tooth (perhaps eaven full row) piston ... It's not crusial, but because it's a support weapon that you only fire full auto you will be stripping the piston faster (because you will be shooting more bb's per game).... So AOE is also an important issue!
Air sealing
http://airsoft.spells.dk/Guides.cshtml?Page=AEGAirSeal_Page1
(Only minor ajustments is needed on the ca 249)
Angle of engagement
http://airsoft.spells.dk/Guides.cshtml?Page=AOE_Page1
This is something you realy should look into! Especialy on that gun... My piston had to be moved back 3.5 mm for a perfect AOE ...
With reguards to the trigger issues:
You can fix it by taking off 1-2 mm of the trigger screw that pushes up the trigger contacts (so it don't push as high) .. and then slightly bend the trigger contacts metal arm down to compensate (Moving the metal contacts arm 1-2 mm away from the gears) ... Then clean the contacts inside (just pop the contacts box open and polish off the burns) ... ....
Then add a mosfet so you don't burn the contacts any more ... Then you don't need to replace the contacts
I did this om my own CA m249 (and also on my AK 249 para) and both have been shooting perfect without trigger issues after
