You can use that one,but trying to get a fet in the buffer with it will be a verry tight squeeze.You could also go the AWS Stealth trigger fet,but tuning the trigger is a real pain.
I would go with this battery for your application:
http://www.get-reload.com/gp-111v-1000mah-20c-lipo-battery-tplug-p-709.html
Now sure the trade off is 350mah,but this battery is a full 94mm shorter than the Firefox so placing your fet in the buffer with battery will be easier.This is the battery I use for similar apps.In my G3 and AR-10,both firing over 500fps,I can just manage to get 4 high caps of shooting out of this battery.Thats quite a bit of semiauto shooting IMO.Nicest part of all,for the price of one of the Firefoxes,you can essentially buy two of these.
I would go with this battery for your application:
http://www.get-reload.com/gp-111v-1000mah-20c-lipo-battery-tplug-p-709.html
Now sure the trade off is 350mah,but this battery is a full 94mm shorter than the Firefox so placing your fet in the buffer with battery will be easier.This is the battery I use for similar apps.In my G3 and AR-10,both firing over 500fps,I can just manage to get 4 high caps of shooting out of this battery.Thats quite a bit of semiauto shooting IMO.Nicest part of all,for the price of one of the Firefoxes,you can essentially buy two of these.
