ease, reduction of static electricity, flash reduction, etc. By controlling these characteristics, a large number of types of propellants have been developed with burning rates that vary enormously. Some propellants work best in small cases such as the 22 Short or 25 ACP while others perform best in large cases such as the 300 Winchester Magnum.
Even with the use of smokeless powder, the problem of corrosion persisted. The cause was the residue that was produced from the primer that was a mixture that contained potassium chlorate. Because of the resulting corrosion, primers containing potassium chlorate became known as corrosive primers. Some ammunition was loaded with primers containing mercury fulminate and after detonation the resulting mercury reacted with the brass case which caused it to be weakened and thus unsuitable for reloading. In 1927, Remington introduced Kleanbore primers that contained a type of priming mixture that was noncorrosive. In most modern ammunition, the primer contains an explosive known as lead styphnate, but recently primers have been developed that do not contain lead. The motivation behind this is to reduce the amount of lead that is present in the air when firearms are used on indoor ranges. For use in rimfire cartridges, the priming mixture contains 35 to 45 percent lead styphnate, 25 to 35 percent barium nitrate, 18 to 22 pecent ground glass, and 6 to 10 percent lead thiocyanate as well as some other minor constituents. The function of the ground glass is to make the mixture more sensitive to friction when crushed in the rim. On the negative side, the small amount of ground glass remaining in the bore increases the rate of wear so that even though soft lead bullets are used, the bore eventually shows the effects of erosion. A 22 LR barrel will not last indefinitely. One of the characteristics of lead styphnate is that its explosive character is destroyed by oil and some organic solvents. If oil seeps into a case, it may cause the round to misfire. This is one reason for the substantial crimp given to 22 rimfire ammunition, the other being that a heavy crimp is necessary to give the correct “pull” that results in uniform velocities.
Remington ammunition has featured Kleanbore priming for many years as shown on these boxes of 22 LR cartridges from the 1950s.
Hyper-Velocity 22 Ammunition
Over the many years in which it has been produced, the 22 LR cartridge has undergone several changes. Most of these involved minor changes in velocity that resulted from the use of different powders or bullets of slightly different weight or shape. However, a radical departure from the norm occurred in 1977 when CCI introduced a round known as the Stinger. The new round utilized a 32-grain bullet that was driven by a heavier charge of powder that had a slower burning rate than the powder ordinarily used in 22 LR ammunition. To accommodate the larger powder charge, the case of the Stinger was made approximately one-tenth of an inch longer than the normal 22 LR case. The result was a round that produced a muzzle velocity of 1,640 ft/sec and a muzzle energy of 191 ft lbs. A flat trajectory resulted from the high bullet velocity so the effective range of the 22 rifle was increased. Owing to the high-velocity hollowpoint bullet, the new round was explosive in its effect on small pests or unopened cans of pop. The term “hyper-velocity” is generally applied to 22 LR ammunition that produces very high velocity.
Very soon after the Stinger was introduced, Winchester began producing a type of hyper-velocity round known as the Xpediter. This load utilized a 29-grain hollow-point bullet with a muzzle velocity of 1,680 ft/sec which gives a energy of 182 ft lbs. Federal followed suit by introducing the Spitfire which employed a 33-grain bullet with a velocity of 1,500 ft/sec and an energy of 165 ft lbs. The Winchester Xpediter was discontinued after being available for a few years, and the current Federal hyper-velocity load is not designated as the Spitfire although the ballistics are unchanged from that round.
Remington entered the competitive field of hypervelocity ammunition with two offerings. The Yellow Jacket features a 33-grain hollow-point bullet at 1,500 ft/sec giving a muzzle energy of 165 ft lbs while the Viper features a 36-grain truncated cone solid-point bullet at 1,410 ft/sec for an energy of 159 ft lbs. Aguila produces one other hyper-velocity round, and it drives a 30-grain bullet at an advertised velocity of 1,750 ft/sec to give 204 ft lbs of energy. However, the energy drops to only 93 ft lbs at a range of 100 yards. Another hyper-velocity round is the CCI Quik-Shok which uses a 32-grain bullet, but the bullet is designed so that it breaks into four pieces on impact. This produces a devastating effect on small varmints although penetration is generally less than with other types of ammunition.
Although the hyper-velocity ammunition gives dramatic effects at short ranges, the light bullets lose velocity more rapidly than do the heavier bullets used in conventional 22 LR ammunition. The result is that the remaining energy of the hyper-velocity ammunition is approximately equal to that of the slower rounds at a range of 100 yards or so. It is also generally true that hyper-velocity ammunition does not deliver the best accuracy in most rifles. There have been many reports published to verify that conclusion, and based on the results of tests conducted during this work it certainly true. Moreover, the longer cases of the Stinger and Quik-Shok pose a problem when used in rifles with so-called matchtype chambers because the case engages the rifling just in front of the chamber. With match chambers, the rifling extends back to the front end of the chamber so the bullet engages the rifling as a round is chambered. The makers of some rifles having match chambers warn against using the Stinger ammunition in those rifles. Bullet diameter for the 22 Short, Long, and Long Rifle is 0.223 inch.
With all of these developments and those described in the following sections, there can be little doubt that this is an exciting time for the rimfire shooter. More details on the performance of today’s rimfire cartridges will be presented in several later chapters in this book.
22 Winchester Magnum Rimfire (WMR)
As wonderful as the 22 LR is, there are situations where more power is called for. In 1959, Winchester responded to that need by developing a cartridge that utilizes a case that is 1.05 inches in length and has a slightly larger diameter head and body than the 22 LR case (0.291” vs. 0.275” and 0.241” vs. 0.225”, respectively ) . Instead of using a bullet with a heel of smaller diameter that fits inside the case and a bullet that has the same diameter as the case, the new round used a 40-grain jacketed bullet of 0.224-inch diameter. This “magnum” rimfire is appropriately named the 22 Winchester Magnum Rimfire (WMR), and the advertised velocity is 1,910 ft/sec from a 24-inch barrel. With a muzzle energy of 310 ft lbs, the 22 WMR is still the most powerful rimfire cartridge available. From the 20-inch barrel of my Ruger 77/22M, the velocity at 10 feet from the muzzle is below the advertised value by about 75 ft/sec.
The main drawback to the 22 WMR has always been the cost of ammunition. Although some special target ammunition in 22 LR may cost as much as $10 for a box containing 50 rounds, the cost of most of the ordinary types is only $2 to $3 per box. Some promotional ammunition in 22 LR can be bought for around $1 per box. Most of the types of ammunition in 22 WMR sell for $6.00 or more with the Remington Premier selling for around $10 per box. It is simply a fact of life that it costs around 12 to 20 cents per shot to fire a 22 WMR.
Three magnum rimfire cartridges are (left to right) the 17 HMR, the 5mm Remington, and 22 WMR. The 5mm Remington has been discontinued since the 1970s.
Being a larger and more powerful cartridge than the 22 LR, the 22 WMR could not be adapted to most actions that were designed specifically for the smaller cartridge. The actions had to be made slightly longer than those used on regular 22s, but very soon after the 22 WMR was introduced a large number of arms were available to chamber it. Winchester marketed the lever-action Model 9422M, and Ruger offered single-action revolvers with two cylinders, one in 22 LR and the other for the 22 WMR. Marlin, Savage, Anschutz, and others produced bolt-action rifles for the 22 WMR soon after its introduction. Currently, bolt-actions, lever-actions, and autoloaders are available in the magnum rimfire calibers as are many handguns (see Chapters 3 and 4).
The
