The Technoid Says It’s Too Darn Hot…..
It is a fact- shells kick more in summer. Back in his salad days, the Technoid ran across a few cases of International Skeet shells from Poland marketed by the notorious, but aptly named, Pawam Pionki. They came packed in wood and fiberboard crates. They kicked like mules. This was understandable since the horse hair wads also made them smell like equine marshmallows in your local auto de fe. Aside from maximum amounts of recoil and odor, their main trait was sensitivity to temperature. The hotter the weather got, the hotter they got. In winter they produced the odd blooper. In the summer, if left out in the sun, split case heads were the rule. Some of this might have been Poland’s cold war attempt to destabilize the West, but most of it was due to the due fact that the chosen powder/wadding combination was extremely temperature sensitive.
Today’s modern powders, especially those used in hunting loads, are remarkably stable. However, there still is a difference between hot and cold weather performance. Rifle reloaders are particularly aware of increased pressures due to hot weather, but it affects shotshells too. As speed and potency increase with heat, so does recoil. This is more noticeable due to the lighter, less padded clothing worn in hot weather. The end result is that shells do indeed kick more when it is hot. Many savvy reloaders drop their powder charges by a grain or so in summer to keep performance and recoil consistent.