If you have been around precision rifle shooting in the last few years, you are most likely aware of the 147 ELDM. This bullet has helped the 6.5 Creedmoor and PRC explode in popularity. With an extraordinary .697 G1 BC, the bullet is a powerhouse for the 6.5 caliber cartridges.
How good is the 147 though? Recently Bryan Litz released claims that the 147 ELDM ballistic coefficients were varying. He claimed they saw a 2.3% standard deviation in the BC values through the Applied ballistics lab. Since I am currently running the 147 ELDM in my competition rifle, I had to put the numbers on paper to see if this would affect my shooting!
The supplied G7 BC for the 147 is .351. A 2.3% change in BC means the value would float between .351 and .342. When we put those numbers into the Hornady 4DOF calculator, the output gives us 15 inches of vertical deviation at 1000 yards due to BC. That is a significant variation when you do not consider shooter error, rifle error, and muzzle velocity variation!
Shooting at just 1000 yards would prove some data, but it would not take into account how well the rifle is shooting. To cut out as many variables as possible, I decided to shoot 15 shot groups at 100 yards, 500 yards, and 1000 yards.
At 100 yards, we can see how well the bullets are shooting with my particular load. At 500 yards, we could see some variation on a smaller scale. At 1000 yards, though, it should highlight any vertical dispersion from shot to shot. If the BCs vary by 2.3%, we should see an increase in the vertical spread MOA at each distance.
100 YDS - .697 MOA Vertical
500 YDS - .401 MOA Vertical
1000 YDA - .811 MOA Vertical
100 YDS - .73”
500 YDS - 2.1”
1000 YDS - 8.5”
30 shot SD - 5
30 shot ES - 12
With these results, the BC variation of these bullets is not a concern for me. Bryan Litz has tested far more bullets and far more lot numbers than I have, and his results are most likely derived from numerous years of data, so his sample size is far more extensive than mine. But so far this year, I have shot just shy of 3000 147 ELDMs in my PRS, NRL Hunter, and Hunting Rifle, and I will shoot around 6-7000 of them by the end of the year.
With confidence, I can say for all of the shooting I do, the BC variation is acceptable, and I am not missing targets due to any variation.