Rifles in .338-caliber have long been among my favorites. I owned a Ruger Model 77 .338 Winchester Magnum years ago and developed several handloads that performed quite well. But when shooting from the bench, it kicked like a mule. A fellow member of my gun club bought a BAR chambered in .338 Win. Mag., and I helped him work up a good handload for an elk hunt. I'm pleased to report the handload and hunter successfully accomplished their mission.
Another friend traded for a .340 Weatherby Magnum with similar intentions and quickly discovered he and the Mark V's recoil weren't too compatible. We eventually traded off our rifles for who knows what. That same friend encouraged me to pursue my first wildcat-cartridge project. Paul Marquart fitted one of his precision, cut-rifled barrels on another first-generation Ruger Model 77 and chambered it for Fred Huntington's .338-.280 RCBS Improved wildcat. I've developed a pet handload that the rifle really likes. It'll routinely group three 210-grain Nosler Partitions into just over an inch at 200 yards.
Several years later, John Gallagher converted an early World War II M38 Swedish Mauser into a .338-08 scout rifle. It, too, soon proved to be a handy little package that delivered top-notch performance. A couple of years ago, Federal Cartridge domesticated the round, calling it the .338 Federal. Ruger added the new round to the Model 77 MKII's cartridge options, and I promptly ordered the Frontier model.
Soon after the recent short-magnum fad started, I rebarreled a Savage Model 16FSS Weather Warrior for the .338-.300 Remington Short Action Ultra Mag (RSAUM) wildcat. Should someone imagine I'm claiming extraordinary ballistic prowess, none of the above cartridges were my exclusive brainchild. Someone else--often several someone elses--had already done them before me. So considering my previous interests in this caliber, it's not surprising I've already latched onto the latest joint venture between Ruger and Hornady--the .338 Ruger Compact Magnum (RCM).
I received my new Model 77 Hawkeye .338 RCM rifle several weeks before the first production lot of factory ammo was shipped. Not to worry! I'd appropriated--or should I say "liberated"--some prototype factory loads and fired brass after a writer's range demonstration at this year's SHOT Show. Hornady provided a set of reloading dies but hadn't finalized any loading data. Just like with my wildcats, I was left to my own divinations for suitable recipes.
Again, not to worry. The .338-.300 RSAUM is almost identical to the .338 RCM except for the fact that the wildcat's case body is a bit larger in diameter. I measured case capacities (to the mouth) and determined the RSAUM case held about 78 grains of water, whereas the RCM case held approximately 5 grains less. I pulled out my Powley computer and determined a safe starting load for both rounds topped with 200-grain JSP bullets.
Wouldn't you know it? The computer indicated I should use the D-type of IMR powder, which is positioned between IMR-4320 and IMR-4350 on the Powley scale.
Fortunately, IMR-4007 SSC was introduced a year or so ago, and it's advertised as exhibiting a burn rate between 4320 and 4350. It was just what I needed to load the new .338 RCM cartridge.
Before I continue, let me point out that Hornady loads factory RCM ammo with what I refer to as "vanity propellants," as they are especially formulated for a limited application to provide optimum ballistic performance. That's the good news. The flip side of this situation is they aren't canistered powders that we handloaders can buy. So we're stuck with selecting from at least 15 or 20 other propellants with similarly appropriate burn rates.
So far, I've fired about a hundred rounds of factory 200-grain SSTs and my handloads. The average velocity recorded from Ruger's 20-inch barrel with the 200-grain .338 RCM factory loads was 2,850 fps. It matched the velocity printed on the cartridge box and is commendable performance in anybody's book. The handloads were charged with IMR-4007 SSC and another new Hodgdon powder, Hybrid 100V. It's supposed to be slower than H4350 and faster than H4831, which puts it even farther below IMR-4007's position on a burn-rate chart.
Topped with 200-grain JSP bullets, the loading density with either powder is nearly 100 percent. I couldn't measure pressures, but my Oehler chronograph recorded only 2,650 fps for the two .338 RCM handloads. Similar recipes but with three to five percent more powder in the .338-.300 RSAUM (with 24-inch barrel) delivered 2,849 fps, and I don't believe I'm pushing any pressure limits.
That's all for now, but I'm sure there will be more practical information about .338-caliber rifle cartridges to share with you later.