expanding gasket on co2 tank?

[iamacheetah]

Is the o-ring that fits on the co2 tank heat expandable? I was changing out a gasket on my regulator and the oring that sits inside the the brass ring expanded to twice its size the short time it was disconnected. How the hell do I get it back in? Can I stick it in the freezer and shrink it?

 

[brewingkitty]

do you mean between the regulator and valve body? it is usually nylon or a fiber material. if it changed size, you need to replace it. welding supply gives them away with tank fills, but it shouldn't cost more than $.25.