Originally Posted by
athomas
Freezing water expands because of the shape of the molecule. Only a few molecules expand when frozen, and water just happens to be one of them. I'm not sure if there is enough water in paintballs to cause an expansion issue if frozen.
Its not the expansion that causes the problem with the balls. Its that the shell can be more easily manipulated at higher temperatures than at lower temperatures. One problem that does happen with cold or frozen paintballs is condensation. If condensation gets on the shell because the cold ball is placed in a warm environment, then the moisture can cause a lot of problems with the shape of the ball.
Ironically, today I was cleaning out my basement and found a 10 round tube of PMI paint that I had put away in a box back in 1993. It was from a case of 2500 (case sizes of 2000 had just started coming out). It had been through a few days of subzero winter storage in the past. The balls were round and actually broke nicer than when they were new. A few years ago I had a case of Zap chronic that I had stored for years under the same conditions. When I shot it about 4 years after it was purchased (tournaments and field paint only prevented its use), it shot better and broke nicer than when it was new. To this day, that case has been the best paint I have ever shot. The previous 13 case of the same Zap chronic and subsequent dozens of cases of chronic I had shot were nice but not near as nice as the 4 year old stuff.