Unbelted, full-length, short, super short, ultra, short-action ultra. Do you have a handle on all the new magnums that have come along in the last few years? Does anyone? Some serious rifle cranks--and a few overworked ballistics technicians--have undoubtedly acquired some familiarity with most of them, at least as far as accuracy and load development goes. But probably nobody has more than a passing field experience with all of them, because there are just too many of the darned things.

Oh, we might get a chance to take a new cartridge out and kill a deer or an antelope with it, maybe a couple caribou. We call that "field tested," but no two field situations are exactly alike, so one or two good results (or bad) are hardly definitive for the performance of a cartridge or bullet. I don't know at what point we pass from slight familiarity to genuine knowledge, but I'm sure it's somewhere in the double digits of game animals taken. I can lay that claim with a couple of the new cartridges.

The funny thing about our huge numbers of new magnums is that in-depth field experience isn't as important as it may seem. This is because almost none of these cartridges break genuinely new ground in terms of field performance.

Similar Stats

Remington's full-length Ultra Mags develop similar velocity, caliber for caliber, as do Weatherby's full-length magnums. The anomaly is the 7mm Ultra Mag because it has no Weatherby counterpart (Weatherby's 7mm has a case shortened to .30-06 length); its existing counterpart is the 7mm STW. Depending on who is doing the loading (and the chronographing), the Ultra Mags may be a little bit faster thanks to their fatter cases. But the difference isn't significant, and since we already know what 7mm, .308, .338 and .375 bullets do at these velocities, there shouldn't be much mystery.

Similarly, the Short magnums from Winchester and Remington's Short Action Ultra Mags offer about the same performance as existing belted short magnums, whether we're talking .270, 7mm or .30 caliber.

It's difficult to make comparisons as direct with Winchester's Super Short magnums, but the .223 WSSM isn't really faster than the .220 Swift. The .243 WSSM is definitely faster than the .243 Win., although not as fast as the .240 Wby. Mag. So my premise is the same: We've known for years what .223 and 6mm bullets at these velocities will (and won't) do.

Lazzeroni's cartridges are indeed a bit different. Whether short or long, they are all the fastest in their class, but is the performance category really unique? The short Lazzeroni cartridges produce velocities somewhere between the .30-06-length belted magnums from Winchester and Remington and the full-length belted magnums (Weatherby, STW). No mysteries here.

The long Lazzeroni magnums are faster than anything else, including the .30-.378 and .338-.378 Wby. Mags. But are they so much faster as to put them in a different performance category? I don't think so.

So in terms of velocity and energy, the new magnums don't offer anything that's truly new, but that doesn't mean they have nothing to offer. They do have their strengths, and before you buy one of them, make sure you know what those strengths are.

The fact that most of our high-performance cartridges--what we call "magnums"--have worn a belt for the past 80 years is almost an accident of history, based on the success of the .375 H&H and the many cartridges based on its case (full-length, shortened, necked this way and that). The belt itself does not have anything to do with performance and never has.

Historically there have been quite a few high-performance unbelted cartridges--the Canadian .280 Ross, Charles Newton's cartridges, the .416 Rigby, Wilhem Brenneke's 6.5x68 and 9.3x64. The concept has long been there, but for most of us a belt has been synonymous with magnum power.

Like a cartridge rim, the belt is an extremely simple and positive headspace index. This means shoulder fit can be sloppy, which can reduce accuracy. A rimless, beltless, bottle-necked cartridge headspaces on the shoulder. This means the fit cannot be sloppy, and a good cartridge-to-chamber fit contributes to accuracy.

Belted cartridges can be and often are very accurate, and certainly they can be loaded so as to create chamber fit every bit as precise as any unbelted case. But, really, the belt serves no essential purpose, and it takes up unnecessary space in the magazine box.

The shift from belted rimless to unbelted rimless for high-performance cartridges began with proprietary lines such as the Canadian Imperial magnums and Don Allen's Dakota magnums. John Lazzeroni expanded and publicized the concept, and the majors have followed with Remington's Ultra and Short Action Ultra Mags and Winchester's Short and Super Short magnums.

What we think of as standard-length actions are built to accommodate cartridges with .30-06-length cases, about 2.5 inches. "Magnum" actions are built to take cartridges based on, more or less, a .375 H&H-length case, about 2.8 inches. In raw terms, in order to get more velocity than cartridges of these case lengths can produce, you need to burn more powder. Few existing actions can house longer cartridges, but many can handle somewhat fatter cases--especially after you get rid of the belt.

Fatter (and, happily, unbelted) cases have long existed in the .404 Jeffery and .416 Rigby cases. These were wildcatted for years and provided the basis for both the Imperial and Dakota magnums.

The big Lazzeroni case, although unique, is similar in diameter to the .416 Rigby (.585 inch). This case is too wide for some actions, so both the Remington Ultra Mags and Winchester Short magnums use a case similar in diameter to the old .404 Jeffery, base diameter about .550 inch.

Remington and Winchester both "rebate" their rims to a smaller .532-inch diameter, the same as standard belted magnums. Lazzeroni not only uses a case that is fatter still but also keeps a full-diameter rim. Whether the rim is rebated or full diameter has nothing to do with performance, but it does mean that many bolt faces cannot be modified to accept the larger Lazzeroni rim.

The wider case holds more powder. If you can burn more powder you can get more velocity, right? Only up to a point. Depending on case size and caliber, only so much powder can effectively burn and push the bullet down the barrel. When you have more powder than can effectively burn you have reached a point of diminishing return--what we call "overbore capacity."

This is not a great sin and is mitigated by the ever-slower-burning powders coming out. But to a degree it does explain why the 7mm and .300 Remington Ultra Mags aren't faster than they are. They are overbore capacity. Period. Again, this is not a great sin, just a fact.

That said, who does the loading is also important. Remington's factory loads are more conservative than Weatherby's, so on paper some Weatherby magnum factory loads are faster than Ultra Mag loads.

Ultimately, case capacity will tell the tale. Remington's full-length Ultra Mags hold more powder than cartridges based on the .375 H&H case. So as handloading data (and, in some cases, slower-burning powders) become available, the Ultra Mags will have at least a slight edge.

Insofar as the Lazzeroni cartridges are concerned, it's no contest; only Weatherby cartridges based on the fat (and belted) .378 case can give them a run for their money.

Short and Fat

The inherent efficiencies of short, fat cases were learned many years ago. The .308 Win., for instance, is almost a half-inch shorter than the .30-06. It holds a lot less powder and burns a lot less powder, yet it is capable of coming very close to .30-06 velocity levels. How can this be?

The wider a cartridge is in relation to its length, the greater percentage of its powder charge can be reached by the primer flame. This more rapid ignition creates smooth, consistent burning that does a lot to promote accuracy (the .308 Win. is inherently more accurate than the .30-06) and yields a bit more energy per grain of powder burned.

By taking those fat cases and cutting them down, first to short action (more or less .308 Win. length) and then shorter still (as in the Winchester Super Short), the concept is carried even farther.

The short magnums from Lazzeroni, Winchester and Remington achieve an incredible level of efficiency, generating velocities of much longer, belted magnums while burning a whole lot less powder. Winchester's new Super Short magnums build upon that principle to produce their high speeds.

This means several things. First, you can house these performance levels in shorter, lighter and handier rifle actions. Second, you are doing everything cartridge design can possibly do to enhance accuracy. Third, you are burning less powder in the process.

There is also a difference in felt recoil. I cannot fully explain it, but it's there. Perhaps it's that smooth, efficient burning curve. But whatever causes it, I notice a difference in felt recoil between, say, a .300 Win. Mag. and a .300 WSM or .300 Short Action Ultra Mag of similar weight. This difference is not earth-shaking, and if you take advantage of the shorter action and build your rifle shorter and lighter, you have just negated it.

The problem with velocities and resultant trajectories is that the charts can be--and are--slanted to tell whatever story the makers wish to tell. Bullet choice has great impact on downrange velocities, and the barrel length you buy may not be same as the barrel length that generated the data.

I have not yet seen either the short-mag offerings from Winchester and Remington come up to factory figures, and while these cartridges definitely produce similar performance to .30-06-length magnums, with really good handloads the greater case capacity of, say, the 7mm Rem. Mag. and .300 Win. Mag. will certainly surpass their shorter brethren--especially with heavy bullets.

I believe in time the Ultra Mag cartridges will prove to have a clear-cut margin over the full-length magnums based on the .375 H&H case. Again, case capacity will ultimately tell, and the Remingtons have more case capacity.

With Lazzeroni's cartridges there is no argument. I have chronographed a lot of his ammo in several (though not all) different cartridges, and his velocities are almost exactly what his literature says. If anything, his printed data is usually slightly lower than actual results.

The Edge

If there's a real edge to the new magnums it may be their accuracy, but there's no guarantee you will see it. I am convinced that the unbelted, fat and short, fat cartridges are inherently more accurate than their longer, slimmer, belted counterparts. I am also certain that the greater rigidity of the short actions many of these rifles can be housed in also contributes to accuracy.

But does that mean a rifle chambered to an Ultra Mag, Lazzeroni or Winchester Short or Super Short will be more accurate than a rifle chambered to a belted magnum of similar caliber and power? Of course not.

Cartridge design is only one of many factors that influence accuracy. If all things are equal, then a .308 Win. will group tighter than a .30-06, and a .300 WSM will group tighter than a .300 Win. Mag. The problem is that all things are almost never equal; the big-ticket items such as quality of barrel, quality of bedding and consistency of ammunition have the most influence over accuracy.

Even rigidity of action, which short bolt actions do possess, falls behind these three in determining accuracy levels. That said, I continue to be impressed by the out-of-the-box accuracy from all of the new magnums I have shot.

Whether you should plunk down the money to buy one of these new magnums depends on what you want. I wouldn't necessarily trade in a 7mm or .300 magnum that shoots well in favor of the new mousetrap. On the other hand, if you are looking for a new rifle with the performance characteristics of, say, a fast 7mm or .300--or any other distinct capability that you don't have--then I'd take a hard look at one of the new cartridges.

It will be decades, if ever, before the load selection for these new magnum cartridges equals that of our old favorites like the 7mm Rem. Mag. and .300 Win. Mag., but today's load selection is adequate and getting better fast. All the advantages you've heard about with the new magnums are real--although not all will be measurable in each and every rifle. And while these rounds aren't dramatically better than the tried-and-true cartridges we grew up with, they are at least a little better, and I think they're also a whole lot of fun.