New cartridges versus belted magnums.
By
Craig Boddington
A cartridge “belt” is a narrow ridge of case material around the cartridge base, quickly stepping down to the actual case diameter. Throughout the 20th Century most cartridge dubbed “magnum” wore belts, so we came to accept that a belted cartridge was bigger, faster, more powerful.
Around the turn of the millennium, with the introduction of fast, fat-cased unbelted RUMs,, WSMs, and more, cartridge design—and our perceptions—shifted away from belted cases. This has continued, witness the Nosler cartridges, Hornady’s PRCs, and Winchester’s 6.8 Western.
The world’s last belted magnum appears to be the 6.5-.300 Weatherby Magnum, introduced in 2016. Since then, even Weatherby has shifted away from the belt, introducing their 6.5 RPM (Rebated Precision Magnum) in 2019, following up with their .338 RPM in 2022. A rebated rim means that the rim is of smaller diameter than the base, allowing a rifle to house a fatter cartridge. Not a new concept. The first rebated rim cartridge was the .425 Westley Richards, introduced in 1908. Best-known is probably 1963’s .284 Winchester, parent case for the 6.5-.284 Norma, and the Weatherby’s RPMs.
As with bottleneck cartridges with full-diameter rims, most rebated rim cartridges headspace on the shoulder. A headspace index is a critical feature to all cartridge design. Headspace, defined, “is the distance measured from a closed chamber’s breech face to the chamber feature that limits the insertion depth of a cartridge placed in it.” There are multiple ways to skin this cat, but all metallic cartridges have a headspace index mated to chamber dimensions.
Simplest is an exposed rim, mated to a recess at the beginning of the chamber. In the blackpowder era, almost all cartridges were rimmed, perfect for single-shots, fine for tubular magazines. Problematic for box magazines because the rims must be stacked to preclude jamming. There were effective box-magazine rifles for rimmed cartridges, but Peter Paul Mauser’s rimless cartridge proved a better mousetrap, headspacing on the cartridge shoulder. Obviously, the chamber must be cut right to match the case, and the cartridge must be manufactured to proper dimensions. Both were possible in the latter 19th Century, so shoulder headspacing became common and is considered more precise.
Let’s return to the belt. The first belted cartridge was Holland & Holland’s .400/.375 Belted Nitro Express, introduced in 1905, headspacing on the belt, with matching chamber recess The mild.400/.375 didn’t succeed. H&H tried again in 1912 with their .375 H&H Magnum. Its gentle shoulder was inadequate as a headspace index, so the belt was retained. Versatile as well as powerful the .375 H&H became a world standard. In 1925 H&H necked the case down to create the cartridge we know as the .300 H&H Magnum, headspacing on the belt because of its tapered shoulder.
Since then, most belted magnums have used the .375 or .300 H&H case. The primary exceptions are Weatherby’s family of big cartridges based on the .378 case; and Weatherby’s two smallest magnums, the .224 and .240.
“Magnum” comes from a French word for an extra-large bottle of champagne. The British started using it in the blackpowder era for extra-large cases. Over time, “magnum” became synonymous with “faster and more powerful.” And, until the RUMs and WSMs, “magnum” was inextricably linked to a belted case.
Belted cartridges with defined shoulders don’t need the belt for headspacing, as long proven by our too-many unbelted “magnums.” Over time, the “magnum” suffix was clearly over-used. Enough turn-of-millennium unbelted magnums failed that today, manufacturers seem reluctant to use the word. Make no mistake: The Nosler cartridges and the PRCs are “magnums” in every sense we know, with or without belt or suffix.
Not all belted magnums have succeeded. H&H’s .240, .244, and .275 belted magnums are nearly unknown. Neither the .308 nor .358 Norma Magnums ever caught on. Some of Weatherby’s belted magnums have achieve widespread popularity; others have remained primarily proprietary to Weatherby. Remington’s 6.5, 8mm and .350 Rem Mags languish.
Winchester’s 1958 .264 Win Mag was briefly popular, then nearly killed by the more versatile 7mm Rem Mag, introduced in 1962. I still have a .264. Velocity is identical to the 6.5 PRC. Because my .264 has an exceptional barrel, I’ll pit it against any 6.5 PRC for groups.If I wanted a fast 6.5mm with more versatility than the 6.5 Creedmoor, I’d get a PRC, maybe a 6.5-.284, maybe a 6.5 RPM. With almost no new platforms and limited ammo, I can’t recommend a .264 today…unless it was a great deal. For me, I have oceans of .264 brass and good handload recipes. Can’t see duplicating its performance and creating a whole new supply chain issue.
Okay, my beloved .264 is history. However, several tried-and-true belted magnums remain worldwide standards: 7mm Rem Mag; .300 Win and .300 Wby Mag; .338 Win Mag; .375 H&H. All are widely loaded and chambered by most manufacturers. The 7mm Rem Mag was the world’s most popular magnum. The .300 Win Mag now occupies that spot, with the7mm Rem Mag still in second place.
In each bullet diameter, there are newer cartridges with modern (unbelted) cases that are at least as fast or faster. In 7mm: 7mm PRC, 28 Nosler, 7mm RUM. In .30: .300 PRC, .30 Nosler, .300 RUM, plus the belted .30-378 Wby. In .338, .338 RPM, .33 Nosler, .338 RUM, and .338 Lapua, plus belted .340 and .338-.378 Wby Mags. In .375, .375 Ruger and .375 RUM, plus belted .375 and .378 Wby Mags.
Newer cartridges with fatter, more efficient unbelted cases, are touted as being more accurate. Maybe, but in my experience quality of barrel, sound bedding and assembly, and quality of ammunition are more important to accuracy than case design.
Whether chambered to old belted or new unbelted cartridges, a good rifle should shoot well. The newest cartridges have an advantage in that they are, at least initially, offered in the best loads featuring the most accurate modern bullets. Hornady’s Precision Hunter line (PRCs) is awesome stuff and there are no flies on Nosler or Weatherby-branded ammo.
Regardless how good the ammo, a factory load is just one assemblage of components. No predicting what load a given rifle might shoot best. The more loads available to try, the better the odds of finding extra-good results. So, cartridge popularity is a virtue, not a sin. Handloaders can experiment endlessly. Factory load shooters should think about cartridges with limited choices.
New cartridges aren’t all about accuracy. A lot of our new cartridges are designed to be mated with faster-twist barrels intended to stabilize the longer, heavier, super-aerodynamic new bullets. Depends on what you intend to do, just don’t forget that heavier bullets and faster cartridges produce more recoil.
Me, I haven’t jumped heavily into the new cartridges. I concede they are “better,” but I’m neither a competitive nor extreme range shooter. How much better do I need? M trusty .264 is the primary reason I don’t have a 6.5 PRC.
7mm is a different story. I used to hunt extensively with the 7mm Rem Mag. Haven’t had one for years. The 7 Rem Mag’s traditional rifling twist was 1:925. Maxes out at about 175 grains, but when I was using that cartridge, I never shot bullets that heavy. I’m fascinated by the heavier 7mm bullets, so I bought a 7 PRC. So far, accuracy is adequate, not impressive; hope the loading bench makes it better.
I’m more of a .30-caliber guy. Most of my mountain hunting is behind me, much of it done with .300 Wby Mag and, more recently, .300 Win Mag. If I were to start over, I’d get one of the modern cartridges in a fast-twist barrel that would stabilize aerodynamic 220 and 225-grain bullets. Since it’s too late to start over, I’m good with my fast .30s in old, belted magnums…with lots of loads to play with.
In .33, I tried both the .340 Wby Mag and .338 RUM. Awesome performance, too much recoil. I retreated to the old standby .338 Win Mag, fast enough, plenty of power, acceptable recoil.
Similar story in .375. I used both the .375 Wby Mag and .375 RUM. Effective, but recoil too unpleasant. I have also used the .375 Ruger extensively, have both .375 Ruger and .375 H&H rifles. I’ll argue all day long that the .375 Ruger is a “better” cartridge than the .375 H&H: More efficient, fits into a lighter, more compact action. It is also faster and delivers more energy, but not by such a margin that recoil goes off the page. As large-caliber cartridges go, the .375 Ruger is popular, but it will never encroach on the .375 H&H’s worldwide availability.
New cartridges are always fun, may give a bit extra, but long-trusted cartridges still get the job done. Just think about it before you get rid of a traditional belted cartridge in favor of something new. Especially, consider what you intend to do, and how much popularity and resultant availability mean to you.