August 10, 2022
By Scott Rupp
Monolithic bullets— constructed of solid copper or copper alloy instead of a lead core surrounded by a copper jacket—have been around for quite a while. Some hunters use them because they have to due to state regs, and some hunters simply like them because of their excellent penetration and weight-retention characteristics. Hornady has had the monolithic GMX bullet since 2009, and the GMX’s fans include serious hunters within the company itself. In developing the new CX (Copper eXpanding alloy), Hornady’s Seth Swerczek told me they initially set out to see if they could make the GMX better for their own hunting adventures.
Monolithic Bullet Performace
The GMX’s performance window—the velocity at which it will expand to the company’s goal of a caliber and a half—goes down to 2,000 fps. The Hornady guys wanted to extend the range at which the bullet would still be doing that speed, and the only way to accomplish this aside from boosting velocity is improving the bullet’s flight characteristics.
They turned to the Doppler radar system they’d used to develop the ELD projectiles. Doppler allows ballisticians to look at a bullet’s actual velocity essentially foot by foot, which provides a far more precise picture of a bullet’s downrange behavior than ballistic coefficient models do.
Their first step in experimenting with the GMX was to strip it of its cannelures. Cannelures are particularly critical to monolothic bullets because they don’t compress like lead-core projectiles do, and the cannelures keep pressures down by reducing the amount of surface area contacting the bore. Cannelures also give metal stripped off the bullet a place to go, reducing the amount of fouling. But cannelures also add drag, so their number, placement and design matter.
After examining the behavior of the GMX without any cannelures, the team began adding them back, experimenting with their number and shape. In the final analysis, two cannelures with a modified radius produced the best results. If you look closely at a GMX bullet, you can see its cannelures basically have a 90-degree shoulder, whereas the new CX cannelures are more beveled. The CX also incorporates Hornady’s Heat Shield tip. Standard polymer tips can deform due to friction-induced heat, and this deformation changes the amount of drag on the bullet—changing it in a way that’s not predictable. The Heat Shield tip does not deform, and the resulting predictable drag curve allows the CX to be included on Hornady’s 4DOF ballistic calculator, a powerful tool for long-range shooters. In practical terms, Swerczek said hunters can expect to see about a 100- to 150-yard increase in usable range over the GMX.
Hornady Outfitter Ammunition
The CX is being offered as component bullets and is now loaded in the Outfitter line, replacing the GMX. Outfitter includes cartridges ranging from .243 Win. to .375 H&H. And in that list you’ll find such fast-steppers as the .257 Wby. and .300 Wby., both PRC rounds, all three Winchester Short Mags and the .300 Rem. Ultra Mag. That’s by design, as Swerczek noted that ultra high velocity rounds match up well with monolithic bullets. Outfitter ammo features sealed case mouths and sealed primer pockets to keep out moisture. Nickel-plated cases ensure smooth feeding. As Swerczek put it, “It’s the best ‘ultimate destination’ hunting ammunition.”
The elk I killed with the Outfitter 180-grain CX (G1 BC .469) was quartering away at 240 yards. At that distance, the bullet from the .30-06 Savage Timberline would’ve been traveling about 2,200 fps. The bullet entered midrib and penetrated about a foot and a half to lodge in bone on the far shoulder. Recovered weight was 175.9 grains, which is 98 percent of the initial weight. The mushroom measured 0.57 inch, well over the 1.5 caliber yardstick Hornady has set for the CX. In short, the bullet performed exactly as the company expects it to.
Accuracy was mixed in the three rifles I tried. While the CX wasn’t the most accurate bullet out of the Savage (see the feature on it elsewhere in the issue), it still averaged just under an inch. In my Ruger American the CX was in line with how well that gun shoots with most ammo. Its performance in the Remington is the outlier. Previous results for factory ammo in this rifle have ranged from 0.75 to 1.3 inches. With the CX, I’d get two bullets within half an inch, but there was always a flier. I also would’ve expected a higher velocity since the Remington’s barrel is two inches longer than the other two. Something’s going on with this rifle/ammo combo, but I don’t know what it might be.
I’m one of those hunters who does like monolithic bullets for a variety of game, and I’ve used them a fair bit. Not every barrel likes them, but if you have one that does, the CX seems one of the best, most advanced options out there—especially for those who shoot at extended ranges.