Beat the Heat — Keep Ammo Cold During Hot Summer DayThe Summer Solstice will be June 21, 2023. That’s just one week away. July is fast approaching. The summer heat is at its peak. During the hot summer months, it’s crucial to keep your ammunition at “normal” temperatures. Even if your powders are “temp-insensitive”, studies show that pressures can rise dramatically when the cartridge gets hot. This is due to primer heating. Keep your ammo out of the car and truck. Temperatures can reach 140 degrees. In a vehicle that is parked in direct sunlight. Denton Bramwell’s article Pressure Factors – How Temperature and Primer Affects Pressure will help you learn more about the impact of ambient temperature on pressures. In the article, Denton Bramwell uses a pressure-trace instrument to analyze temperature’s effect on ammo performance. Bramwell’s experiments produced some fascinating results. The barrel temperature, for example, was a major factor. Your test results will be significantly affected if you do not take barrel temperature into consideration when performing pressure testing. The barrel temperature has an effect of around 204 PSI/F? Varget load. If you don’t control barrel temperature, it is just as well that you do not control powder temperature. In the cases studied, barrel temperature was a stronger variable than powder temperatures.” This Editor has personal experience with 6mmBR hand-loaded ammunition that was left in the sun for 45 minutes, while steel targets were being reset. The brass was quite warm to touch, indicating that the casings were over 120? The casings were well over 120? The bullets were impacted high at 600 yards when I shot this ammo (compared to earlier that day). I then chron tested the ammo that had been exposed to the sun. I left the ammo in the hot sun for about 3/4 of an hour. The velocity FPS increased dramatically. Keep ammo under cover or in a container that is insulated in the shade. We do not recommend using H20 ice packs in the container. You can use a sealed cool pack. Don’t use the same container for food and drinks. Powder Heat Sensitivity Comparative TestOur friend Cal Zant from the Precision Rifle Blog published a fascinating test comparing four powders. Hodgdon Varget H4350, IMR 4451 and IMR 4166. The first two powders are Hodgdon Extreme, while the last two are from IMR’s Enduron propellant line.The testers measured powder velocity over a wide range of temperatures, from 25? The testers measured the velocity of the powders over a wide temperature range, from 25? F. Hodgdon’s H4350 was the most temperature stable powder tested. [NOTE: New Alliant Reloder’s TS 15.5 also proved to be very temperature stable in AccurateShooter range tests.]
Tags: Cal Zant Powders, Enduron Powders H4350, July Temperatures, Powder Heat Sensitivity Blog, Varget
