Often a dilemma presents itself while Im out shooting with a .22 rimfire. Whenever I come across a rat, feral pigeon or the like, the vicinity of the farm buildings prohibits its use. The trouble is, there is too much glass and property to damage for me to use a rimfire, even with subsonic ammunition, and some shots may be pointed skywards, which would prove very dangerous. An air rifle would be a better bet but I now carry a spare magazine containing reduced- velocity .22 rimfire ammunition, which can be a real godsend in a situation where a .22LR rifle is too dangerous or just plain overkill.
There are various manufacturers offering reduced-velocity ammunition, such as Eley, CCI, RWS and Remington, to name but a few. They come in various guises, ranging from the pipsqueak BB cap to the .22 CB Long Round not Long Rifle (LR). Compatibility is no problem as the .22 long cases can function in rifles designed to take .22LR cases, but the BB and CB caps should be manually loaded to avoid jams or malfunctions. This raises another important point in that, while it is perfectly safe when firing shorts in a LR chamber, accuracy and fouling in the chamber may become an issue. Therefore, it is advisable to buy a small quantity of each type of round so as to ascertain which works best in your own rifle. This should be mandatory, as each rifle has its own unique preference for one variety of ammo anyway.
Lets go through each of the available ammunition types and discuss their strengths and weaknesses. First, there are two rounds that can be treatedtogether the BB and CB caps. Basically, these resemble an LR case cut down to approximately one third its size and still retaining its rimmed base, with the projectile lightly crimped at the top as normal.
The BB cap design I tested was a variety from RWS. They come in a plastic container of 100 and are marked 6mm Ball Breech Caps (though designated as 6mm they are .22 calibre). I weighed a sample of five of the round ball projectiles and the average was 15.5 grains. At first glance, it looks as though it couldnt knock over a tin can, let alone a rat. However, from my Anschutzs 14in barrel, this little cartridge leaves the muzzle at an astonishing 887fps, which generates 27.1ft/lb of energy more than capable for any barnyard pest foray. Accuracy was less impressive with the little XIV carbine only capable of about 1.5in to 2in at 20 yards.
Enough to despatch your quarry cleanly if correct shot placement could be guaranteed, though, in reality, for the test rifle, I would limit their use to no more than 20 yards. In fact, 10 yards around the farm buildings is a more practical distance and accuracy was far better. An alternative to the BB cap is the similar CB cap, which has identical case dimensions but possesses a conical projectile instead. The RWS CB cap has a sharp, pointed conical bullet weighing 16.1 grains (based on the average of five). Muzzle velocity is a little higher, at 959fps, which gives a muzzle energy of 32.9ft/lb, making the CB cap a good choice for close-range vermin control when it is safe to do so.
In the test rifles, the conical bullet shape fared better than the round BB cap projectile, but with groups of 1in to 1.5in at 20 yards this rounds effective range as with the BB caps is 20 yards maximum from the right rifle, though 10 yards is more practical. Remember that light bullets soon shed their energy as compared with heavy bullets at the same velocity therefore making them safer to use but still be sure of a secure backstop.
Next comes the more conventionally shaped .22 ammunition the .22 CB longs, which offer very useful ballistic properties. They give you enough knock-down power to despatch a rabbit and their low velocity makes for very quiet muzzle report without a sound moderator and inaudible with one fitted.
Accuracy is greatly improved, due to the more conventional design, as there is less bullet jump from the cartridge to the start of the rifling in the barrel compared with the BB and CB caps. This would invariably lead to inconsistent, less accurate shots than if a bullet is seated close to, or just off, the lands of the rifling.
These shoot a 29-grain solid bullet at 705fps and give 32ft/lb energy. Potentially they should shoot more accurately and indeed they did.The Anschutz shot really well out to 20 yards, maximum 0.75in groups with 0.5in clusters at 15 yards were the norm. Their long case designation means that they can be magazine-fed from most rifles.
CB longs would be my choice out of the bunch but Eley also produces a Zimmer indoor or room in German round, based on the LR case configuration and so would have the best functionality in the rifles magazine and chamber. These have a 40-grain bullet which sped across the chronograph at a pedestrian 797fps giving 56.4ft/lb. Though giving a reasonably higher energy figure than the other cartridges, it is worth remembering that the bullet is a solid lead projectile and will have a tendency to ricochet on any hard surface so make sure there is a soft, safe backstop if using these rounds. Accuracy was very good and 20-yard groups were below 0.5in, but even at these velocities there will be marked trajectory curve, so if you intend to shoot them through the same rifle as your normal .22LR ammunition, check the zero at five, 10 and 20 yards to learn where to hold off or adjust your scope turrets.
Finally, a very unusual cartridge the Super Colibri round from Aquila, manufactured in Mexico and distributed in this country by York Guns. This round utilises a conical projectile of 20 grains weight (19.8 grains based on the average of the five weighed) but uses no gunpowder and only relies on the propulsion from the primer mixture. An LR case is used but it is designed to be shot from short barrels and hence the Anschutz XIV 14in barrel was used in testing. This round is best limited to 10 yards, which is more than enough range around the farmyard and, indeed, accuracy tests showed one-hole groups at five yards, 0.75in to 1in at 10 yards and nearly 2in at 20 yards. With an energy of 16.5ft/lb, you have more than enough oomph to despatch vermin both fur and feathered.
First, each reduced cartridge has its own place in the .22 hierarchy. The BB and CB caps possess limited hunting potential but with minimal over- carry, making them good for close-quarter vermin shooting. While the CB longs have true hunting characteristics at restricted ranges, all the ammunition was very quiet in operation, which was a great bonus. But caution must be taken with these rounds with regard to ricochets resulting from the non-expanding nature of the ammunition. The Super Colibri are very short-range loads from short-barrelled rifles, but they fill a niche with their low noise and minimal over-penetration, and reduced ricochet risks.
Eley Zimmers are a good transitional round from standard subsonics to lower velocity rounds, as the LR case does not cause any fouling in the chamber and functions better through the magazine. However, it does have a reasonably high velocity with a heavier bullet so over-penetration could be an issue, especially without a hollowpoint design. My advice is to try a few rounds in your own rifle and enjoy the quieter things in life.