The one point(I think) that has not been addressed in this thread as well as other threads in the past is the role of the primer. When the temperature get low, the efficiency of the primer deteriorates on two levels. One is the thermal heat sink issue of the primer stuck and surrounded by the metallic shot shell rim. When the temperature gets lower, the lead staphinate (primary explosive)will ignite as well and as quickly as at higher temperature. However, if the primer cup is cold, a substantial amount of the brisance (explosive umph for a lack of better terms)is disipated by the cold copper/brass cowling about the primer cup. I've taken a chunk of dry ice and placed the shot shell base on it for a few moments, enough to get it frosty without cooling down the powder which is insulated by the base wad. Then I stuck it quickly in the gun, so it did not have time to heat up substantially and pulled the trigger. Bloobers or no ignition (WW shells). I haven't done this, but what would be cool is to take the upper part of the shell containing the shot and the powder, wrap it with cloth and ice or dry ice for a bit while keeping the base brass warm and see what happens. Grant it that it isn't too scientific, but this might be an interesting Armbruster like approach to study ignition, shell pressure and fps analysis using a chronometer with different primers and powders.
Iggy
