kjw m4 with mapp (propylene) gas?
 

has anyone used MAPP gas (propylene) in their kjw m4 version 2? anything break?

and if so ... what temperatures? and any other tips.
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I use it for colder weather games, works well in 0 to -10 weather.
Don't have a kj but no issues in various WE and KWA guns.

As for tips, cold weather is hard on parts. makes plastic and metal brittle. Also MAPP gas runs $12-$17 a can.

As stated, it does work in colder temperatures much better than propane. Significantly less cool down. If my stock WE M4 can handle it then I'd imagine your KJ would work without issue. One thing to note is that if you dislike the smell of propane, your going to hate MAPP, it's pretty smelly.

what are your thoughts on 1-8 degrees celcius. not negative. i notice my propane suffers in those temperatures let alone negative temps.

Like others said, its fine (if you can handle the stench). In warm weather it'll have a bit more pressure than propane but in cold weather it will run okay and not lose as much power as propane does in sub 5C weather. It also isn't as prone to the effects of cool down (when firing auto, for example), including in cold weather.