In my quixotic quest for a simple answer to the military cartridge question, I have learned a great deal about one of my favorite metric cartridges, the 6x45mm.
My search for the answer started a few years ago. I had just completed a successful South African safari and had a day or two left before heading home. I was planning on taking a few photos or working on an article when the PH came to the breakfast table with a slick little mini-Mauser in his hands and a smile on his face. "Would you like to go cull some impalas, Greg?" he asked in his thick Afrikaans accent.
Always ready for a little trigger time, I wolfed down the rest of my breakfast, grabbed my pack, and followed. Shortly, we were playing cat-and-mouse in the thorn brush with a herd of impalas. "Take the one at the back, Greg," Pieter ordered.
I found the ram's tawny shoulder in the scope, touched the trigger, and watched the ram drop in its tracks. It took me a second, but I realized that the rifle hadn't moved when I touched the trigger. I looked over at Pieter and noticed his mischievous smile.
"That's a 6x45, Greg," he said. "She's a sweet-shooting little rifle, and she'll get the job done if you do your part."
Another dozen impalas later, I had to agree. The easy-on-the-shoulder cartridge was downright deadly on game and an absolute blast to shoot.
Simply put, the 6x45mm is a 5.56x45 cartridge necked up to accept a 6mm bullet. Though its limited case capacity precludes it from working well with heavier bullets, it propels 85-grain bullets at pretty close to 2,800 fps with ease. It's no laser beam, but the 6x45's mild-mannered power appeals to me.
A few years later, in a discussion with friends about alternatives to the 5.56x45 for military use, I was reminded of the deadly little pop gun. After a few adult beverages, we decided we had solved all the world's problems, including that of the "woefully underpowered" 5.56mm cartridge. The answer, we concluded, was the 6x45.
At the time, the 6x45 seemed like the perfect choice. After all, we reasoned, with nothing more than a new barrel, the military could up firepower significantly with a cartridge that would drive 85-grain bullets at 2,800 to 2,900 fps. So to test my theory, I shipped off my .223 Remington Model Seven CDL to Hill Country Rifles to be rebarreled.
While my rifle was gone, I combed the usual sources for good reloading data. There was no shortage of data, but it didn't exactly grow on trees, either. And as I investigated further, I noticed one glaring issue: a lack of match-grade and big-game 6mm bullets in the 80- to 85-grain weight range, which I believe offers the ideal mix of velocity and bullet weight in this chambering. Remington's 80-grain PSP and Sierra's 85-grain HPBT looked promising, so I ordered a quantity of each and started loading. By the time my rifle got back, I had several loads ready to roll.
I asked that the test rifle's barrel be lopped off at 20 inches. Though 22 inches would have handled just as nicely and given me a bit more velocity, I started this project with the AR platform in mind, so I went with a shorter barrel thinking it would give me a more realistic idea of what kind of velocities I could expect. With a trim, little Nikon 2-7X attached, the rebarreled Model Seven was a slick-handling, attractive package.
On the range, my first loads shot well enough and showed no signs of excessive pressure. I tried several loads before settling on the two most accurate ones. Both were slightly below maximum, but not by much. H335 was the powder of choice.
The first load pushed Remington's 80-grain PSP at a disappointing 2,755 fps. The second drove Sierra's 85-grain HPBT at 2,701 fps. Velocity fell a bit short of the 2,800 fps I had really hoped to achieve, but the 100-yard accuracy was phenomenal with both loads.
Before delving deeply into the numbers, I carried the little rifle afield to test its lethality the only way I know how--by shooting a bunch of cull deer of various sizes from a variety of angles.
Over the course of five trips to the ranch and to the leases of several friends, I shot a dozen deer ranging from smallish does to a 160-pound buck--a brute down in my neck of the woods. I didn't notice a difference in performance between the loads. Regardless of angle, size, and distance, all expired pretty quickly. Three deer--a medium-size buck and two does--dropped in their tracks. The others ran between 25 and 150 yards after being hit.
The buck that ran the farthest was shot too far back by a friend's son. My tracking dog, Tuffy, found it in short order. Though the buck was stone dead, that incident pointed out the Achilles heel of the 6x45: penetration. The tiny case just doesn't hold enough powder to drive the heavy-for-caliber bullets to the velocities needed to ensure deep penetration.
Later, the computer did an even better job of pointing out the little 6x45's weaknesses. A closer look at the included comparisons will show that its moderate velocity and the low sectional density of those 80- to 85-grain bullets combine to dash my hopes for the military success of the 6x45. They start out with a slight advantage, but as you can see in the chart on page 28, those light-for-caliber bullets run out of steam quickly. I will continue to tinker with my loads, but I don't think I'll see an appreciable velocity gain, and I think heavier bullets would be counter-productive.
Although my computer and range work crushed my hopes of military acceptance for the 6x45, that sharp dose of reality did little to curb my enthusiasm for the 6x45 as a sporting cartridge. After all, it is a light-recoiling, super-accurate round that's fun to shoot, easy to load, and more effective on game than the .223. That's more than enough to guarantee the 6x45 a place in my permanent collection.