major complaint about the 22 WMR has centered on the subject of accuracy. It is popularly believed that the 22 WMR does not give accuracy that is quite the equal of that given by the 22 LR and some newer rimfire rounds. This perception may be in error, but that topic will be addressed more fully in later chapters.
5mm Remington Magnum
In 1970, Remington unveiled a rimfire magnum cartridge that offered even better performance than the 22 WMR. However, that cartridge deviated from the usual rimfire caliber because it was a 5mm or 20-caliber (actual bullet diameter is 0.2045”). The 5mm Remington Magnum cartridge produced 2,100 ft/sec with a ballistically efficient 38-grain bullet. As a result, the muzzle energy was 372 ft lbs, and the remaining energy also exceeded that of the 22 WMR at longer ranges. The 5mm Remington used a case that is slightly larger in diameter than that of the 22 WMR. Remington produced the Model 591 (box magazine) and Model 592 (tubular magazine) boltactions, but these were the only rifles produced for the 5mm Remington cartridge. Thompson/Center produced barrels chambered for the 5mm Remington to be used on the single shot pistols that they market. The 591 and 592 were discontinued in 1974 with a total of approximately 50,000 having been produced. The 5mm cartridges have become highly collectible with prices for a full box often being in the $50 to $75 range or more.
With greater energy and flatter trajectory than the 22 WMR, the 5mm Remington may well have been the best rimfire cartridge in modern times. Although the trajectory is not quite as flat as that of the 17 HMR with a 17-grain bullet, the 5mm Remington with its 38-grain bullet is a far more powerful cartridge. Part of the difficulty with the 5mm stemmed from the high pressure, which may have been as high as 35,000 lb/in2. The high pressure caused the case to expand into the extractor notches, which necessitated some changes in the chamber, bolt face, and extractor grooves. Given the propellants available today, it is likely that the remarkable ballistics of the 5mm Remington could be produced with a somewhat lower pressure. Moreover, there are several rifles available today that could probably serve as platforms for the excellent 5mm Remington cartridge. The Ruger 77/22M, Anschutz, Remington 504, CZ 452, and Kimber models come to mind immediately. We can only hope that rifles and ammunition in this outstanding rimfire caliber become available once again. If not, a 20-caliber cartridge based on a necked down 22 WMR case but utilizing the superb Hornady V-Max polymer tipped bullets would be very interesting and useful. Given the fine rifles that are available in 22 WMR caliber, it should be a simple matter to produce a 20 caliber cartridge based on that case.
17 Hornady Magnum Rimfire (HMR)
Perhaps no other new cartridge has generated so many printed words in such a short time by so many writers as the 17 HMR. Introduced in 2002, the 17 HMR was the first new rimfire cartridge since the short-lived 5mm Remington. However, the 17 HMR certainly will not suffer a similar fate! The number of rifles and handguns available in 17 HMR caliber is very large. This is natural because the 17 HMR case is simply a 22 WMR case necked down to hold a 17-caliber bullet. Therefore, a firearm designed around the 22 WMR can be made into a 17 HMR simply by changing the barrel. Even the magazines that hold 22 WMR cartridges will feed 17 HMR cartridges. Because so many firearms in 22 WMR caliber were already in production, there are now many that are also produced in 17 HMR.
Nominal bullet diameter for the 17 HMR is 0.172”. The original load consisted of a 17-grain Hornady V-Max polymer tipped bullet that was loaded to a velocity of 2,550 ft/sec giving an energy of 245 ft lbs. The well-shaped bullet has a ballistic coefficient of 0.125 so it holds velocity well which results in a rather flat trajectory that makes hits on small pests possible out to 150 yards or more. Although many larger varmints have been taken with the 17 HMR, the cartridge is at its best when used on species like ground squirrels, crows, pigeons, and prairie dogs. Early reports by some writers described the use of the 17 HMR on species as large as coyotes, but many reports have also described failures of the tiny bullets on larger pests like groundhogs, foxes, and coyotes. One of the most interesting discussions on the 17 HMR is that by C. Rodney James which was published in Gun Digest 2005. In an article published in the February 2005 issue of Predator Xtreme, Ralph Lermayer has related some of his experiences on the failure of the 17 HMR as a cartridge for use on larger varmints. Recently, loads employing 20-grain hollow-point bullets having a muzzle velocity of 2,375 ft/sec have been introduced to reduce the explosive character. This ammunition may help reduce bullet fragmentation, but the tiny 17 HMR was never really intended for use on larger species of varmints. Nonetheless, the 17 HMR is a great little cartridge that gives outstanding accuracy, and we will have a lot to say about it in other chapters of this book. Incidentally, it was the development of suitable propellants that made the ballistics given by the 17 HMR possible. Had such propellants been available at the time the 5mm Remington was introduced, the 17 HMR might never have been developed.
Calibers available to the rimfire shooter are (left to right) the 17 Aguila, 17 Mach 2, 17 HMR, 22LR, and 22 WMR. Although all are useful, each has its advantages and disadvantages.
Introduced in 2004, the 17 Mach 2 is gaining wide acceptance. Note the mention on the label of the “first production run” on this box.
Two cartridges that the author (and many others) would like to see brought back are the 5mm Remington (left) and the 25 Stevens (right).
17 Mach 2
The 17 HMR represents a 22 WMR case necked to hold 17-caliber bullets, but consider the potential of a 22 LR case necked to hold a 17-caliber bullet. An enormous number of rimfire rifles could become 17-caliber rifles simply by changing the barrels. In order to produce a cartridge that would hold enough powder to give a high velocity, the case used could be that of the CCI Stinger which is 0.700 inch long rather than 0.600 inch of the normal 22 LR. These procedures are exactly those used by Hornady and CCI to produce the 17 Mach 2, which launches a 17-grain bullet at 2,100 ft/sec (which is approximately twice the velocity of sound hence the name Mach 2).
However, there is a potential problem with simply changing the barrels on 22 LR semiautomatics. The new 17 Mach 2 burns more powder than a 22 LR so the chamber pressure remains high for a longer period of time. This causes the bolt to be driven to the rear at higher velocity than when 22 LR cartridges are fired. To keep the bolt from being driven back with enough force to damage the action, a heavier bolt must be used or a stronger recoil spring or both. There is no problem with bolt-action 22 LR rifles becoming 17 Mach 2 pieces, but in the case of autoloaders, changes other than merely switching barrels may be necessary.
Firing a 17-grain bullet with a muzzle velocity of 2100 ft/sec, the 17 Mach 2 produces a muzzle energy of 166 ft lbs. This is less power than that produced by some high performance 22 LR rounds so the 17 Mach 2 is a rifle for small pests. Accuracy as good as that produced by any rimfire is the strong point of the 17 Mach 2. With its flat trajectory, small pests are in danger out to around 125 yards when the shooter does his or her part. However, two of the last three boxes of 17 Mach 2 ammunition that I bought cost $6.99 each while the other was $5.99. This is approximately two or three times the cost of good quality 22 LR ammunition and is about the same as 22 WMR ammunition. The difference probably would not matter to a pest hunter, but it certainly would to the casual plinker.
17 Aguila
A recently introduced 17-caliber cartridge is known as the 17 Aguila. While the 17 Mach 2 utilizes the longer CCI Stinger case necked to hold a 0.172 caliber bullet, the 17 Aguila employs a 22 LR case of normal length. Powder capacity of the 17 Aguila is less than that of the 17 Mach 2 so a muzzle velocity of 1,850 ft/sec is produced with a 20-grain bullet (remaining velocity at 100 yards is 1,267 ft/ sec). However, bolt-action
