It is common knowledge that many factors affect the flight of your bullet. Many shooters spend a lot of time and energy taking barometric pressure readings, ambient temperature readings, worrying about Coriolis effect (Spin of the earth) and Spin drift (spin of bullet), all issues that affect the bullet path. But, these same guys do not consider their ammo sits out in the sun or is buried between their sandwiches in the backpack. The ATAC long range shooters are always looking for ANYTHING that has an effect on bullet flight.
One of the most important factors that affect the burn speed of the propellant in your cartridge, and in turn, the muzzle velocity of the bullet exiting your barrel is cartridge temperature. What was your ammo temp when you zeroed your rifle? I bet you probably documented everything else, including how many coffees you drank on the way to the range.
I was at the range the other day and a fellow shooting next to me was telling me that his rifle usually shoots low for about the first hour he arrives at the range. Then, after an hour or so the rifle shoots zero. I asked if he didn’t mind filling me in on exactly what was his procedure on getting ready to go to the range. He looked at me as if I was a little crazy. He told me that he loaded all his gear in the truck the night before. I asked including ammo? He said sure I don’t want to forget anything. So now he sits with all his ammo lined up like soldiers in a row sunbathing in the bright sunlight. In Northern Arizona, nighttime temperatures during the spring are usually in the 40’s. The cartridge temperature in the sun was 88 degrees after an hour in sunlight. Don’t think it makes any difference? You better test it for yourself and know first hand what/how these seemingly small things can affect those bullets headed down-range.
On your next outing to the range bring a iced cooler with 5 rounds in a waterproof container. Let another 5 rounds sit in the sun for ½ an hour or so. Then, shoot these rounds back to back, you may be very surprised. I often carry 5 rounds in my pocket for this reason. Try it for yourself, and you might find out that IT DOES MATTER!
by Lawrence Bolton
Venom Tactical and ATAC Staff