Q. I have a .308 Win. Remington 700 rifle I would like to take elk hunting. I’m thinking about using Hornady’s Superformance GMX ammo. The factory loads both the 150-grain and 165-grain GMX bullet in this caliber. Which one would you choose for elk?

– Tim Yoder, Dallas, TX


I’ve owned and tested a number of rifles in .308 Win. over the last 40 years and have developed more than 90 handloads for this caliber. This taught me that the 150-grain bullet offers the best balance of velocity and energy in this cartridge. The problem is that until recently, 150-grain .308-caliber bullets have had mediocre ballistic coefficients.


 .308 Win. Superformance ammo

Hornady’s .308 Win. Superformance ammo with the 150-grain GMX bullet produced an average muzzle velocity of 2,960 fps. This load’s 2,917 ft/lbs of muzzle energy makes it the most powerful .308 Win. load that Dr. Topper has ever used.

Fortunately, things have changed. A number of companies now produce very streamlined bullets for the .308 bore. Hornady’s 150-grain GMX and SST bullets both have ballistic coefficients of .415, which allows them to take full advantage of the velocities that can be developed from the .308 Win. with 150-grain bullets. The 165-grain GMX and SST have even higher B.C.s, but launching them from a .308 Win. case gives up nearly 200 fps in velocity, compared to the 150-grainer. Because the GMX is constructed of solid gilding metal and retains almost 100 percent of its weight after impact, it should give adequate penetration on just about any big-game animal in the Lower 48 States.

I recently tested the Superformance 150-grain GMX in a 22-inch Thompson/Center Dimension rifle and in a 24-inch T/C Icon. Velocity was 2,898 fps from the 22-inch barrel and a blazing 2,960 fps from the 24-inch barrel. At that velocity, the bullet from the 24-inch barrel produced 2,917 ft/lbs of muzzle energy, which is well within .30-06 levels of performance.

The Icon was very accurate with the GMX and fired a 4.75-inch five-shot group at 300 meters. I aimed about 8 inches high, and the group hit dead center. To confirm trajectory, I then fired a three-shot group aimed at the center of the target. This group was only 2.5 inches across and just 6 inches low. None of my handloads ever performed this well.


– Dr. Martin D. Topper


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