Gear > Ammunition

Hornady GMX Bullet

The GMX is destined to become one of the most respected hunting bullets on the market. 

Last year I shot a buck with Hornday's new "expanding solid" bullet. In addition to recharging my freezer, I was granted the opportunity to evaluate the bullet's performance on game. The GMX is non-toxic and California-compatible, but it's also a high-performance bullet for hunting.

One whitetail is not a conclusive test of any bullet, but it does give some indication of what to expect. The path of destruction through the buck was impressive: It started by smashing the near shoulder, passed through at an angle and exited behind the ribs on the far side. Expansion clearly started early and the wound channel grew large, creating massive damage to the lungs, which indicates a large frontal area with good energy transfer. Finally it exited, which I expect from a big-game bullet.

The concept of a monolithic (defined as one homogeneous piece of metal) expanding bullet is hardly new. Barnes developed the idea and introduced its X-Bullet 20 years ago. Legendary terminal performance coupled with emerging social factors that have demonized lead (e.g. the green movement) have created a growing market for this style of
hunting bullet. Hornady has decided to step into the arena.

The new Hornady bullet is called the "Gilding Metal eXpanding" (GMX), which gives a clue to what monolithic metal is used. Gilding metal is the same material most jacketed bullets use to wrap the lead core, an alloy composed of 95 percent copper and 5 percent zinc. Gilding metal has more lubricity than pure copper and has been found to produce less metal fouling and lower bore friction than copper. It is malleable enough to expand without breaking, but tough enough to resist further shape change once expansion is completed. It has been the standard for jacketed bullets for generations and is proving to be a very good choice for monolithic, expanding bullets.

In general these types of projectiles exhibit very high weight retention-they have no core from which to separate, which aids in penetration. They open early, but once the expansion reaches the solid shank below the hollow cavity in the nose, the expansion stops. Plus, because gilding metal is much tougher and far less malleable than lead, the bullet retains its shape during penetration, and this keeps it on a straight course.

The downside of a monolithic bullet is the cost, which is typically much higher than a traditional lead-core bullet; also, because the specific gravity of the material is lower than lead, the bullet will be longer in any given weight. To meet the specified cartridge overall length they must be seated deeper into the case, which robs powder space. This is critical in some cartridges, but not all.

In years past, monolithic bullets had some other problems, but they are fading away as technology evolves. Because the bullets are longer and much harder than lead-core bullets, they caused internal pressures to spike earlier, therefore they had to be loaded with less powder and so produced slightly less velocity. Also, monolithics often had fouling and accuracy issues; however, the new designs have all but eliminated those problems.

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