The Effect of Barometric Pressure On Shooting
BY Herschel Smith
4 years, 5 months ago
For example, consider a rifle chambered in 6.5 Creedmoor, the ammunition loaded with a 140-grain Hornady ELD Match bullet. Muzzle velocity is 2,710 feet per second, and the rifle is set with a 100-yard zero.
At the same altitudes, but at very different barometric pressures, the bullet drop between these two scenarios is significantly different. For an extreme example, Ballistic Pro Shooter Logan Brown notes that at a high barometric pressure of 30.00 versus an extremely low pressure of 25.00, the difference in the above bullet’s trajectory at 1,000 yards can be nearly 30-inches. That’s huge!
Best advice: Logan says to update your Atmospheric Conditions on Ballistic as you move from place to place, and as weather fronts move in and out. Ballistic will automatically recalibrate your projectile’s trajectory based on the atmospheric inputs and changes to those inputs, placing you on target no matter the conditions.
He doesn’t give units, but he means 30″ Hg (to be precise, 29.92″ Hg). And I’ve seen lower than 25″ at the top of Mt. Mitchell before, plenty of times (in the 22″ – 24″ range).
I’ve never loaded this app, but it makes sense to become familiar with it if you’re going to shoot during conditions not similar to where you zeroed your rifle.
On July 21, 2020 at 2:47 am, JB said:
I use DA(density altitude)