"Improved" Rifle Cartridges

By Chuck Hawks

The late writer, gunsmith, experimenter and wildcatter Parker (P.O.) Ackley probably did more to popularize the notion of the "Improved" rifle cartridge than anyone else, although many others have been involved in the development of such cartridges. Roy Weatherby also comes to mind, as his .220 Rocket is an Improved .220 Swift, the very successful .300 Weatherby Magnum is an Improved .300 H&H, and the .375 Weatherby Magnum is an Improved .375 H&H.

An Improved cartridge is merely a fire-formed (blown-out) version of a standard caliber. Typically the Improved cartridge has less body taper, a shorter neck, and a sharper shoulder than the original. This increases the case's powder capacity and hence the muzzle velocity (MV) that can be achieved with a given weight of bullet at a given pressure. There is, as they say in the automotive world, no substitute for cubic inches.

Of course, recoil and muzzle blast also go up, and efficiency typically goes down--the price of increased performance. And it should be obvious that only strong, modern rifles should be considered for conversion to Improved calibers. Do not attempt to Improve any rifle based on a weak or ancient action, such as a "Trapdoor" Springfield, Krag, or pre-Model 98 Mauser. These actions were not designed for the high (usually 52,000 cup) maximum average pressure (MAP) at which most improved cartridges operate.

Because Improved cases are created by firing standard cartridges in an Improved (reamed-out) rifle chamber, it stands to reason that, in a pinch, standard factory loaded cartridges can be fired in an Improved rifle. For instance, .257 Roberts cartridges can be fired in a .257 Improved rifle and .30-06 cartridges can be fired in a .30-06 Improved rifle.

There are Improved (wildcat) versions of a great number of standard rifle cartridges, from the little .22 K-Hornet to the .375 Weatherby Magnum. For the shooter who yearns to own a wildcat rifle at moderate cost, an Improved cartridge is the easiest way to go. All that is really required is to have the chamber of a standard caliber rifle reamed-out to the improved dimensions and the purchase of a set of special (Improved) reloading dies. Cases to reload are then fire-formed in the chamber of the improved rifle from standard brass.

The subject of "Improved" cartridges is a somewhat controversial one. The fans of the type claim that they give a standard cartridge near magnum hitting power, while the detractors scoff and observe that while there is certainly extra expense and effort required to own and feed an Improved rifle, there is little or no real world performance benefit.

In this case, I suspect that both sides have caught at least the tail end of the truth. Of course, there are better and worse Improved rifle cartridges. Some do offer meaningful performance benefits, usually in terms of flatter trajectory and increased maximum point blank range. Others seem more like exercises for those with too much time on their hands.

The skeptics and detractors have a point, as it is hard to see how most Improved cartridges offer any meaningful increase in killing power. If you can reliably and humanely kill a particular game animal with an Improved cartridge, you probably could have killed the same animal with the standard version of that cartridge.

In other words, Improving the .257 Roberts, which in my opinion is one of the best of the Improved breed, does not take it out of the class of CXP2 game cartridges. It just makes it a somewhat flatter shooting CXP2 cartridge.

The .257 Roberts Improved is my idea of a worthwhile Improved cartridge, since the standard .257 Roberts, at least until the advent of .257 +P loads, has always been under loaded by the major ammunition manufacturers. Remington set the maximum average pressure limit for the standard .257 Roberts at 45,000 cup instead of the 50,000-52,000 cup of most high intensity cartridges. (For example, the 6mm Remington, based on a necked-down .257 case, is pegged at 52,000 cup.)

The .257 Improved is a real improvement over the standard (low pressure) .257 Roberts. A .257 Improved loaded to a MAP of 52,000 cup will usually deliver MVs 100-300 fps faster than the standard cartridge loaded to a MAP of 45,000 cup. And the Improved cartridge (unlike a standard .257 cartridge reloaded to a MAP of 52,000 cup) cannot be chambered in a standard rifle, eliminating any liability concerns. The latter is a valid point in our tort-crazy culture.

Other Improved rifle cartridges that have had a run of popularity include the .218 Mashburn Bee, .22 K-Hornet, .22-250 Ackley Improved, .243 Ackley Improved, .280 Ackley Improved, .30-30 Improved, and .30-06 Improved. Of these, the .218 Mashburn Bee, .22 K-Hornet, and .30-30 Improved (along with the aforementioned .257 Roberts Improved) were probably the most useful, as they offered a worthwhile ballistic advantage over their standard counterparts without requiring the purchase of a new rifle for a more powerful cartridge.

Unfortunately, the introduction of the .222 Remington put the .22 K-Hornet and .218 Mashburn Bee on the skids. And the advent of .257 Roberts +P ammunition makes near 257 Improved ballistics available to all owners of modern .257 Roberts rifles, which bodes ill for the future of the .257 Improved.

The same could be said of the .30-30 Improved and the .307 Winchester, except that many older Winchester and Marlin .30-30 rifles are probably not suitable for conversion to .307, but could be usefully upgraded to .30-30 Improved should their owners desire to do so. In any case, Winchester and Marlin are no longer producing new .307 rifles, so the .30-30 Improved remains a useful wildcat.

The .22-250 Improved offers a worthwhile performance increase over the standard .22-250, but that just results in duplicating the performance of the .220 Swift and .223 WSSM, which are available factory loaded. Likewise, the .243 Improved (loaded to 52,000 cup) barely exceeds the capability of the 6mm Remington or .243 WSSM and falls short of the performance of the .240 Weatherby. Simply buying a rifle for one of the factory loaded 6mm cartridges would seem to be a better way to go.

The .280 and .30-06 Improved fall into that controversial area where it can be argued that the increase in performance is simply not worth the trouble. For hobbyists who like the idea of an Improved cartridge and don't mind reloading all of their ammunition, they are fine. For everyone else the standard cartridges are quite sufficient.

The most successful Improved cartridge of all time is the .300 Weatherby Magnum. The .300 Weatherby is probably the biggest case that makes any sense for a .30 caliber cartridge (if indeed any .300 Magnum cartridge can be said to make sense). It started life as a proprietary wildcat designed by Roy Weatherby, who created it by fire-forming .300 Holland and Holland brass in a .300 Weatherby chamber.

Weatherby's big .300 struck a responsive chord with shooters, became the most popular of the Weatherby calibers, and has been used to take all classes of game worldwide. It went on to become a SAAMI standardized cartridge and is now available from most major ammunition manufacturers. As such, it is truly the Improved cartridge that made good!

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Copyright 2005, 2013 by Chuck Hawks. All rights reserved.