Cartridge for competitive shooting

The idea behind the caliber was to pack more performance into a compact, practical cartridge that fits directly into the most common rifle action: The aim was to create a new and accurate cartridge for competitive shooting, with less bullet drop, more wind resistance and a smaller recoil. The recoil is relevant because, in many competitive forms of the sport, you shoot against a time limit at a fast pace. Less time needed for recovery from the recoil gives a direct competitive advantage. The cartridge should work in all disciplines up to 1,000 yards, easily and practically. The reloaders were not forgotten either: the reuse of the cartridges should be at a reasonable pressure level, and the components needed for reloading should be reasonably priced.

The result was a new caliber 6.5 Creedmoor – 6.5 CM – pressed into the outer dimensions of the 308 Winchester cartridge, with a ballistically affordable and readily available 6.5mm bullet size. The Creedmoor appears to be a shortened and necked 308 Win cartridge, but it is not. Its cartridge is a .30 T/C necked down to 6.5mm, the "30-06 performance in a smaller package" cartridge introduced by the Thompson Center and Hornady in 2007. The .30 TC has the same nominal cartridge diameter as the 308 to one hundredth of a millimeter, but has slightly straighter sides and a slightly higher CIP operating pressure than the 308W cartridge.

Soon after its introduction, the 6.5 CM started winning competitions and quickly found its way into the long-range "tactical" shooting scene, which is gaining popularity in the USA. The chosen 6.5mm / .264 bullet is ballistically a good compromise between bullet weight and cross-sectional area, offering a much smaller bullet drop than the 308W caliber. There are a number of precision and hunting bullets available in the popular bullet size from many manufacturers, so the versatility of the cartridge was good immediately.

Increase in performance

The nominal length of the 6.5 CM cartridge is only 0.64mm longer than the 308W (CIP), so it will work without any problems with all 308Win magazines. It also works directly in self-loading rifles such as the popular 7.62 AR guns. Almost any 308Win rifle can be upgraded to 6.5 CM caliber with a simple barrel change, which also significantly lowered the threshold for gun manufacturers to offer a new upgraded caliber.

Compared to the 308Win cartridge, the 6.5 CM offers about 20% more performance in terms of both bullet drop and wind resistance. At the same time, the recoil is reduced by about 30% – all important features for competitive shooters, long-range rifle shooters and equally desirable for birding and other hunting. In practice, a 6.5 CM precision rifle with a good muzzle brake is somewhere between small and non-existent. Based on shoulder feel, it would be hard to believe how much performance it actually offers compared to 308 Winchester.

So the cartridge was performing right from the start, but performance is rarely enough to justify global success. Many a good cartridge has been forgotten without similar success. Creedmoor was no exception; an important part of the final breakthrough was the immediate availability to shooters of a range of accurate, high-performance and affordable factory cartridges.

The 6.5 PRC

The 6.5 PRC is one of the newer additions to the short 308 Win cartridge range. Released in 2012, the cartridge was the result of a collaboration between GAP, a precision rifle manufacturer from Missouri, USA, and Hornady. Also, the basic idea of this cartridge was to offer more performance in terms of drop and wind resistance for a "Short Action" rifle size, more than the performance of the 6.5 Creedmoor.

The target group for the PRC was thought to be precision rifle shooters. The name "Precision Rifle Cartridge" refers to a shooting sport that has grown in popularity in the USA over the last decade, where small targets hundreds of meters away are shot at high speed against the clock and from applied positions. With time being a particularly important component of good performance, the direct benefit of a small recoil is great. As in the cartridge of the 6.5 CM, a faster bullet with better ballistic efficiency gives the competitor a margin of error in both elevation and wind correction. A ballistically better and faster bullet is less susceptible to wind-induced misses.

With a larger cartridge capacity and higher pressure level performance was raised to a higher level, at least one order of magnitude better than the Creedmoor. A cartridge with a mere speed advantage would have been easier to achieve with 6mm bullets, but then the ballistic efficiency of the bullet would have suffered too much. The range of bullets in .25 / .270 is much smaller, and the larger 7mm / .284 caliber bullets did not reach the target velocity for the short rifle action. Optimizing any cartridge for drop and windage is always a properly optimized balance of bullet ballistic efficiency, muzzle velocity and desired range.

In the light of the numbers, the 6.5 PRC is a sort of "6.5 Creedmoor Magnum", offering more of everything in the same bullet size: The 6.5 PRC's cartridge capacity is approximately 18% larger than the Creedmoor and the caliber's main cartridge is a .300 Ruger Compact Magnum rated for higher pressures than the Creedmoor.

So you can get at least one order of magnitude more in practical performance from a short rifle action than the 6.5 Creedmoor – but unlike the Creedmoor, the cartridge is not directly compatible simply by re-barreling. However, most short actions are suitable for the caliber with only minor modifications, so adding a cartridge to an existing production rifles does not usually require major investments or completely new rifles from manufacturers. The nominal length of the 6.5 PRC cartridge is 2.955" / 75.06mm – a couple of millimeters longer than the maximum cartridge length of typical 308W magazines. The 6.5 PRC cartridge is 1.5mm / 0.059" larger in diameter than the Creedmoor and 308 Winchester, requiring a magnum-sized bolt head and a magazine that feeds a 300 WSM-size cartridge.

In the 9g/140gr bullet weight class, the 6.5 PRC factory loadings have a muzzle velocity advantage over the 6.5 Creedmoor of about 6–8%, a clear increase of about 50–70m/s. So in practice, the 6.5 PRC is evenly matched by the 6.5x284 Norma caliber, which is considered to be a very high-performance cartridge. However, with quite long bullets offering good ballistic efficiency, the 6.5x284 requires a long action when loaded to its nominal length, meaning the 6.5 PRC offers the same performance in a much more compact rifle size.

But everything has its price

More powder burned, higher pressure and heat mean faster barrel erosion. When firing full-power cartridges, the best accuracy of the 6.5 Creedmoor barrel is about 1.5...2x longer than the 6.5 PRC. However, the best accuracy shot count for the 6.5 PRC with full power loadings is still in the four digits, which means that it's not really a problem for competitive shooters who are looking for top performance and constantly maintaining their equipment. In hunting use, the number of shots is typically much lower, so even a modest barrel life compared to the 308W will still be years, even decades, in practice. The way the gun is used can also have a big impact on the life of the barrel. Long, fast-paced bursts of fire without cooling breaks will wear the barrel out much faster. There are also differences in the type of powder used – although usually the shooting style and other maintenance of the gun have a much greater impact on the life of the gun than the quality of the powder. Self-loading can have other effects – maximum pressures and the final push with muzzle velocities will wear out the barrel much faster than a slight drop in “daily use” load. The effect with even modest drop of peak velocity on can mean up to double of shots as accuracy life of the barrel. Usually, however, the first sign of erosion of the cartridge chamber is not lost accuracy but reduced muzzle velocities.

Of the two calibers compared, Creedmoor has already secured its place for the future through its huge popularity. It remains to be seen whether the 6.5 PRC can do the same. Probably not – but it is already popular for good reason. Its popularity will continue to grow with those wanting excellent ballistic performance in a compact "short action" - sized rifle package.

Everything can always be improved, but the 6.5 PRC is not far from the practical limits of a typical short rifle action in terms of cartridge diameter, at least if the caliber change is made directly from the current 308 Winchester / 6.5 Creedmoor production rifles. Burning an even larger amount of gunpowder behind a small 6.5mm bullet would further reduce the accuracy life of a barrel. Only a few hundred rounds with best accuracy may be too short for many gun owners who appreciate convenience.

But as the performance race continues, anything is possible: the 300 Remington Short Action Ultra Magnum is also a 308 Winchester-sized cartridge. It would be rated for a slightly larger cartridge capacity and an even higher pressure level. As wildcat, it is already in use as a 6.5 SAUM cartridge.