hello, the engines of our rifles batteries can withstand up to 12 volts .... but not all mechanical ...!
usually the case as the g & g, classic army, ics, system, g & p, etc. .. have reinforced mechanical series, but sometimes these brands wrong assembly, and when mounting the battery voltage with high bub .... ... gears or pistons are to be fuck!
for mechanical guns, low cost advice I always 8.4 ... obviously not what you buy with the gun ...
however soon open a topic where you can see some good batteries.
advice on your gun mount the 8.4 race