[Ninja_En_Short]

For CO2 mags, either the WE or the GHK for the WA system, they both need some tweaking to work how they should.
Plus, if you go for an M4 I strongly advise you buy an RS wrench for the stock ring and barrel nut, they hard to screw properly without that.

For the high FPS semi thing, no, I use a GBBR (G36 right now, worked fine at -1 degree Celsius with gaz mag by the way) because I like using semi only (and I put 5/6 round on target in 2 seconds anyway ) and AEG are in any way as responsive as a GBBR, plus without MOSFET they have a tendancy of getting stuck in the middle of cycle when I shoot fast in semi.
One thing that works well in winter with gas mag : put a chemical warmer in your pouch or tape one on the mag, with the temperatures we have it will keep it around 20 degree, it will be perfect