from my experiences with co2, its as finicky as greengas. you really should only use co2 and green gas in spring/summer time. But if you use HPA you can use it in ANY temp range.
also keep in mind your psi dosent really matter too much if you don't have volume.When you run CO2 at a cold temp you should still be fine as even at Freezing temp 0C (32F) CO2 still has a pressure around 475 psi. That is before the regulator, so if your regulator is set to 150 psi and your CO2 is at 475 psi it should have no problem maintaining the 150 psi output. Unless you are firing at an insane rate like 8 bb's a second insane.
If you are getting liquid CO2 past your regulator then that is where you are having problems. If there is Liquid CO2 in your line and it starts to expand that is the time where you could possibility start shooting very hot. As it can expand up to its highest pressure depending on temp ( 850 psi @ 21c[75F], 475 psi @ 0C[32F] ). But your regulator will prevent liquid CO2 from entering into your lines or gun so your good on that point.
Hmm, I never noticed this when I ran my rig on the KJW M700. What do you think it could be?also Co2 creates a grayish film in your internals thats another reason why i stop using Co2 and switch to HPA