Most wax bullets have a melting point of between 135 degrees to 150. At 150 they are a puddle. At 135 they maintain their shape but will squish between your fingers. That means you have an equal chance they will spit rather than exit the barrel whole. Our high temp bullet has a squish point of 185 degrees. The Deputies of Upland, Ca. tested them by putting them in casings, in a clear plastic case, on a black cloth, on a table in the middle of an asphalt parking lot, in the direct sun on a 112 degree day for their entire five hour shoot. At the end they loaded and fired them. The casings were almost too hot to handle. Every bullet was shot, hit the target, and they did mushroom when they hit.
To give you an idea. If you put your shells on the dashboard of your vehicle, on a 90 degree day, windows up, leave it facing the sun, in about two hours the temp will be around 150 degrees. Figure about 50 degrees hotter than the outside temp. At this temp your bullets are mush.
Try our high temp bullets and forget about the heat and sun. Still fast and accurate.