THE BELTED CARTRIDGE

Cartridge case design can be classified in various ways, but one of the primary methods involves the design of the cartridge base. Thus, we assign labels such as rimmed, rimless, rebated rim, and belted. That latter design, the belted cartridge case, is interesting enough to look at in detail.

Belted cartridge cases are easy to recognize as they have a pronounced band of "extra" brass surrounding the circumference of the base. It's typically about 0.222-inches in height and has a diameter about 0.020-inches greater than the case body.

USEFULLNESS

The history of belts on cartridge cases goes all the way back to 1905 when they were first used by Holland & Holland. Although they have been successfully used for more than a century, in recent times, it's been fashionable to trash the belt as a useless appendage that serves no purpose other than to limit magazine capacity and promote feeding problems. As with most broad generalizations, there is some truth to that, but there's a lot of error as well. The error usually originates from a lack of understanding of headspace, a critical measurement ensuring a cartridge fits properly and safely in a rifle's chamber.

Modern centrefire cartridges with a pronounced shoulder measure headspace from the base of the case to an arbitrary datum line somewhere on that sloping shoulder. However, if the shoulder is not pronounced, or missing altogether (as in straight wall cases), there needs to be some other provision for determining headspace. The only other options are rims, belts, or the case mouth itself. Of these three, the belt is a reasonable option that works well.

Note that we haven't mentioned how the belt makes for a stronger case, one able to take higher pressures. That's because this is a myth originating from the association we all make of belts to "Magnum" cartridges. The reality is they provide no more case strength than can be legitimately achieved through non-belted case design. Yes, this means belts have been used as marketing devices to help sell the idea that certain cartridges are legitimate "Magnums." And as we all know, for some hunters, if you're not using a "Magnum," it's impossible to kill any game animal. So, in certain cartridges like the .375 H&H, .458 Winchester Magnum, and others, the belt is needed as the means of controlling headspace. However, on others, including the 7mm Remington Magnum and .300 Winchester Magnum, the belt is more of a marketing feature as these cartridges have a pronounced shoulder and could be headspaced to that dimension. However, this use of the belt in marketing seems to have waned significantly, judging by the design of the newest crop of magnum-level cartridges. Numbers like the .33 Nosler, .338 Lapua, and .375 Ruger all get along fine without a belt.

NEGATIVES

An accusation commonly leveled at the belt on magnum cartridge cases is that it impairs smooth feeding from the magazine in bolt-action rifles. I'll be the first to admit it doesn't do anything positive for smooth feeding, but I'm not so sure it's enough of an impediment to reliability to cause real-world problems. After all, the .375 H&H is a popular and celebrated African cartridge, in a place where unreliable feeding doesn't just result in a lost animal, but potentially in a lost hunter.

Remember that the belt was designed as a replacement for the rim in the commonly encountered rimmed cartridges of the day. Rimmed cartridges have a reliability issue if the operator makes an error in loading the magazine and the rim of a top cartridge ends up locked across the rim of a lower cartridge. This rim-lock effect jams up a rifle very effectively. I've tried to create this jam with belted cartridges, but I've never been able to duplicate it. In a properly designed rifle and magazine, I don't see the belt as posing a reliability problem, and I'd argue history agrees.

The other criticism, the one about limiting magazine capacity, has slightly more justification. That belt does add to the effective width of belted cartridges and certainly consumes usable magazine space. Whether eliminating the belt would allow one more cartridge in the magazine is, however, questionable, simply because a belt just doesn't add a lot of width to each cartridge. In a typical magazine, we'd have to remove a lot of belts to make room for one more full-size cartridge.

HANDLOADING

Hunters shooting factory ammo exclusively have few concerns about using belted cases as they toss their empties aside. Handloaders, however, have some issues when reloading belt-equipped cartridges.

The biggest issue arises with belted bottleneck-shaped cases like the common 7mm Remington Magnum. Because belted cartridges headspace off the belt, and since resizing a case doesn't change the belt dimension, handloaders tend to ignore shoulder setback during sizing. The combination of high-pressure loads in magnum cartridges and too much shoulder setback leads to case head separation, which is the inevitable result of brass thinning just forward of the belt. And in as few as three or four firings, the head of the case breaks loose from the case body, leaving the latter firmly stuck in the rifle's chamber.

The key to preventing this is to acquire and use the tools needed to measure shoulder setbacks occurring during reloading and monitor any thinning effect so brass can be tossed in the garbage before head separation happens. Forster's Datum Dial is the tool I use to measure shoulder movement, as it provides accurate results, is reasonably priced, and uses a digital micrometer I already have (forsterproducts.com). A bore scope is the best tool for inspecting the inside of cartridge cases to see if any thinning is happening just above the belt, but a simple probe with a small hook at the end can be made from a paper clip. By dragging the hook along the inside of the case wall near the belt, any thinning will be felt as a groove inside the case.

And one more thing. Magnum level cartridges naturally use slow-burning powders with or without a belt. Using the appropriate powder types and quantities as outlined in a trusted handloading manual is important. Drastically reduced amounts of slow-burning powder can create wild pressure spikes capable of destroying a rifle and earning the shooter a visit to the hospital emergency room. During my forensic career, I had the chance to examine two rifles where this happened. About the only salvageable part in both cases was the recoil pad. So, be careful, belted case or not.

As you can see, belts on cartridge cases can be necessary features or they can be marketing add-ons. They aren't as popular as they once were, but there's no need to give up on cartridges featuring them. Some of the finest chamberings ever developed wear them proudly.

ABOUT THE AUTHOR

Al Voth calls himself a "student of the gun." Retired from a 35-year career in law enforcement, including nine years on an Emergency Response Team, he now works as an editor, freelance writer, and photographer, in addition to keeping active as a consultant in the field he most recently left behind—forensic firearm examination. He is a court-qualified expert in that forensic discipline, having worked in that capacity in three countries. These days, when he's not working, you'll likely find him hunting varmints and predators (the 4-legged variety).