Little mind-boggler, spyder/bolt orings on co2 question

[PBCapo]

I was thinking about it. When you're shooting a spyder (or a variety of guns) in cold weather with co2, it'll freeze up. I always assumed this was because the bolt o-rings expanded and stopped the bolt from moving, but why would anything expand due to lack of heat, i thought things expand when heated.....hmm

[peewee]

The cup seal gets hard & wont seal venting air down the barrel.

[Coralis]

Correct me if im wrong (like that has to be said) but Orings tend to swell when they absorb liquid CO2, kinda like a sponge absorbing water