The Gun Digest Book of .22 Rimfire. James E. House

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 rifles and most autoloaders that fire 22 LR cartridges can be converted to 17 Aguila caliber simply by changing the barrels. Even though the 17 Aguila produces slightly lower velocity than the 17 HMR, the difference is not enough to make any practical difference in hunting use especially since the 17 Aguila uses a 20-grain bullet. Shots should be limited to somewhat shorter ranges with the 17 Aguila, but both are suitable for small game and small pests. The almost unknown 17 High Standard cartridge is apparently almost identical to the 17 Aguila.

      Newest of the rimfire cartridges is the 17 Agiula, which is a 22 LR case necked to hold a 17 caliber bullet.

      Although several obsolete rimfire cartridges have been interesting and historically important, the choices available today make this the most exciting time in rimfire history. Hopefully this will become more apparent as you read this book.

      In 17 HMR, Hornady markets loads with a 17-grain polymer tipped bullet (left) or a 20-grain hollow-point (right).

Chapter 2 SAFE SHOOTING

      Anything that launches projectiles has the potential to cause injury. This is not limited to slingshots, bows, airguns, or firearms. Golf balls, baseballs, and horseshoes have all caused fatalities. In baseball, batters wear helmets for a reason. Participants in other sports wear protective equipment. However, it is in the shooting sports that safety must be paramount. Firearms launch small projectiles at high velocity so they can travel great distances. In spite of this, it entirely possible to enjoy shooting sports for many years and fire tens of thousands of shots in complete safety even though the news media may routinely consider that anything involving a firearm is a high risk activity. In this chapter, we will describe some of the aspects of safety that shooters must follow in order to participate safely in shooting sports.

      Aware of the safety issues related to the storage of firearms, Sturm, Ruger & Co. include a safety lock with most of their products.

Devices and Programs

      We are at a point in time when shooting accidents are occurring at the lowest rate they have been for many years. There are several reasons for this welcome decline. First, currently produced rifles and pistols are manufactured with more safety features than ever before. Let me cite just one example. Older single-action revolvers can fire accidentally if dropped or the hammer is struck a blow because in some cases the firing pin is an integral part of the hammer and it rests against a cartridge. In other models, the firing pin is held permanently in the frame, but the hammer rests against the firing pin. In either of these types of single-action revolvers, the firing pin may be held away from the cartridge by a notch on the hammer (a so-called safety notch). That safety notch may not be adequate to keep the firing pin from striking the cartridge if a substantial blow to the hammer occurs. In order to carry such a revolver safely, it is necessary to keep an empty chamber in front of the firing pin. Old timers knew this and their revolvers were treated as “five shooters” rather than “six shooters.”

      Single-action revolvers are those that require cocking the hammer for each shot (which also rotates the cylinder) and this type has been popular for about 150 years. In 1973, Sturm, Ruger, & Company redesigned its single-action revolvers to produce the “new model” single-action. After the new model revolver is cocked, a transfer bar moves upward to a position between the hammer and the firing pin only as the trigger is pulled to the rear. Therefore, only if the trigger is pulled will the hammer strike the bar and transmit the blow to the firing pin. Neither accidentally dropping a new model revolver nor a blow to the hammer will cause it to fire because when the transfer bar is down, the hammer rests against the frame and it is not in contact with the firing pin. These “new model” revolvers can be carried safely with all six chambers loaded. This is just one example of the additional safety features that are found on some newer firearms.

      While the situation described above is in reference to single-action revolvers, it also existed for some of the familiar lever action rifles with their visible, manually operated hammers. Most newer lever action rifles have safeties that block the hammer