The .375 H&H case holds about 85 grains of water (to the base of the case neck). That means the .375 Ruger case capacity is about five grains more. I set the Powley at 90 grains of water to determine the estimated powder-charge weight, which was 77 grains. So, the charge to bullet weight ratio for a 270-grain bullet is 0.285. I aligned that with the sectional density of 0.275 to figure out which powder to use, and the Powley scale pointed to the "D" powder. That means between 4320 and 4350. According to the instructions, I should add five percent to the indicated charge weight and load 81 grains of the slower-burn-rate powder, IMR-4350, with a 270-grain bullet.

When I reset the charge weight to revise the charge-to-bullet-weight ratio, it was 0.3. The length of the barrel was 21 inches to the base of the bullet, so I aligned that number with the .375-caliber index, and the expansion ratio read between 7 and 7.5. I flipped the Powley computer over, set the charge-to-bullet-weight ratio to 0.3, and the velocity read 2625 fps on the expansion ratio scale.

Comparing that data with what the new IMR Data Center website recommends for the .375 H&H reveals 78.5 grains of IMR-4350 as a compressed charge with the 270-grain Remington bullet to yield 2710 fps at 53,000 CUP. Hornady's 7th edition manual shows a maximum load of 76.3 grains with the 300-grain FMJ bullet. Because the .375 Ruger's case capacity exceeds the H&H by six percent, I decided to start with 78 grains under the 270-grainer and work up carefully.

Fortunately, I spoke with Mitch Mittelstaedt at Hornady before I began loading. I commented that the .375 Ruger's increased case capacity would allow starting with higher .375 H&H load data.

"Whoa, Lane," Mittelstaedt cautioned. "That's not so. I had the same idea at first, but when I tested several handloads, chamber pressures ran nearer to max than I anticipated. Apparently, the .375 Ruger's shorter powder column improves the round's ignition efficiency enough to shift the burn rate a bit faster. I actually measured the same or a little higher velocities with slightly less charge weights than comparable .375 H&H loads."

I took his advice and started with lower- end .375 H&H load data. The accompanying chart shows my results with Ruger's African Hawkeye rifle. Of course, my handloads have not been officially pressure-tested, so if you choose to try them, start five percent below the listed charge weights to be safe.

Will the .375 Ruger be another outstanding cartridge success story? At this point, I don't know. What I do know is that the round really packs a wallop--at both ends of the rifle.