Accuracy and the .22 Long Rifle
October 23, 2018
This article took no longer to write than any other, but the accuracy tests that are its subject took a while to complete. Anyone who has worked seriously with the rimfire .22 Long Rifle cartridge knows the slightest breeze can push a bullet off course by a surprising amount. Four squeezes on the trigger can put four bullets through virtually the same hole and then a light puff of air on your cheek as you squeeze off the fifth shot tells you there is no point in looking through the spotting scope because you know that bullet went astray.
When top-tier match rifles, such as those built by Anschutz, Bleiker, and Walther, are matched with their preferred ammunition, they are capable of consistently shooting five bullets inside 0.250 inch at 50 yards. The same also goes for some of the rifles put together by custom builders. Shot dispersion at various distances is an angular measurement, so average group size at twice that distance should be less than 0.500 inch, and that is possible when shooting on an indoor range. But the 40-grain bullet of the .22 LR has a low ballistic coefficient (.140), and when shooting outdoors, it is easily pushed around by nothing more than a light breeze.
Several years ago I tried my hand at small-bore metallic silhouette competition with an Anschutz 54MS wearing a 24X Redfield 3200 scope. While seeking the most accurate ammunition for my rifle, I bench tested loads made by Eley, Lapua, RWS, CCI, and Federal. Five, five-shot groups were fired, and range conditions were near perfect with the flags indicating only occasional light breezes. When moving from 40 to 77 meters, group size averaged 2.8 times larger (the smallest increase among the various loads was 1.6 times, the largest 3.9 times). Mostly due to the breeze.
A solution to the problem is to shoot indoors. Few of us have that option, so the only choice is to squeeze off groups outdoors when there is little to no wind. In order to accomplish that, one of the three rifles I used for this report always accompanied me on trips to the range, regardless of whether a Model 1911 in .45 ACP or a rifle chambered for the latest centerfire cartridge was on the schedule. If range conditions proved favorable, I shot the .22 rimfire until wind flags told me to retire it.
Over a period of several weeks, I shot groups that were true indications of rifle and cartridge accuracy. It is important to note that the accuracy shown in the chart is not necessarily for five consecutively fired groups.Three Rifles, Three Tests
Three different series of tests were performed. One was to shoot different manufacturers’ lots of the same brand of Lapua match ammunition in an extremely accurate rifle to demonstrate accuracy differences between those lots. The rifle used was built for BR-50 .22 rimfire competition, and it has a single-shot Remington 40X action, a Jewell two-ounce trigger, and a McMillan benchrest stock with a 3.0-inch-wide fore-end. Its stainless-steel Pac-Nor Super Match barrel is 22.5 inches long, measures 0.950 inch at the muzzle, and has five-groove rifling at a twist rate of 1:16 inches and bore and groove diameters of 0.2170 and 0.2221 inch respectively. Its chamber was reamed to match dimensions.
Another series of tests compared the accuracy of Eley match ammunition with other types, including standard-velocity, high-velocity, and subsonic ammunition. The custom rifle used for those tests has a Ruger 10/22 receiver and magazine, Volquartsen components, and a Volquartsen trigger. The Lilja match-grade, stainless-steel barrel is 18.75 inches long, measures 0.980 inch at the muzzle, and has a 1:16 twist. Bore and groove diameters are 0.2170 and 0.2215 inch respectively, and it has a Bentz chamber. Its colorful Boyds laminated wood stock was shaped specifically for shooting over sandbags.
The third series was fired with a bolt-action Ruger American Rimfire, which was included to represent off-the-shelf rifles used by millions of shooters. It has a 24-inch barrel with the usual 1:16 twist. As is typical for hunting and plinking rifles, it has a standard-dimension sporting chamber. Squeezing top accuracy from match ammunition requires a tight-dimension chamber, and while it can sometimes deliver good accuracy from a sporting chamber, the difference is seldom great enough to justify the higher cost compared to run-of-the-mill ammo. It can even be less accurate.
When shooting the 40X and the 10/22, I used a Heavy Varmint front rest from Sinclair International. The fore-ends of both rifles have flat bottoms, and while the 40X is wider, the width-adjustable sandbag platform of the rest easily accommodates both. The fore-end of the Ruger American stock is quite narrow, so with it I used a Brownells Bulls Bag resting atop a Lyman height-adjustable Bag Jack. The targets, Birchwood Casey’s Eze-Scorer 12x18-inch Multiple Bull’s-Eye, proved to be perfect for the job. Regardless of whether I was loading magazines for the 10/22 and Ruger American or loading the 40X single shot, an SB-200 Rimfire Ammo Box from MTM was quite useful.Match Chambers Versus Sporting Chambers
Mass-produced hunting and plinking rifles commonly have sporting chambers, the dimensions of which are “looser” than the match chambers of precision-built bolt-action rifles. As a cartridge is pushed home in a match chamber, its bullet is fully engaged by the rifling. That along with a diameter closely matching the diameter of the .22 LR case more closely aligns the axes of the bullet and bore than in a sporting chamber. The match chamber is not often seen in bolt-action rifles used for hunting small game because with the bullet wedged tightly into the rifling, some rifles may occasionally fail to extract a loaded round should unloading become necessary, such as when crossing a fence or for other safety reasons. Few of us carry a cleaning rod in the field, so if that happens the rifle can be unloaded only by firing it in a safe direction.
The Bentz chamber is to semiautomatic rifles and pistols what the match chamber is to bolt actions. Its dimensions are tighter than those of a sporting chamber but looser than a match chamber. The bullet of a chambered cartridge rests closer to the rifling than in a sporting chamber, but rather than fully engaging the rifling as in a match chamber, it usually rests just short of the rifling. The match chamber is not used in autoloaders because it would increase the possibility of slam-firing due to the bullet-to-rifling engagement resistance of a cartridge entering the chamber. Regardless of the type of action used, the Bentz is an excellent choice for a custom hunting rifle because in a quality barrel accuracy can be almost as good as from a match chamber.
Due to their longer cases, CCI’s Stinger and Quik-Shok ammunition should be fired only in a chamber with sporting dimensions or in a custom chamber sized specifically for them. Chambering one of those cartridges in a match or a Bentz chamber forces the mouth of the case hard into the rifling leade, and that increases the grip of the case on the bullet for a dramatic increase in chamber pressure. The same applies to Aguila Super Maximum and other ammo that have cases longer than standard for the .22 LR cartridge.To Clean or not to Clean
Opinions on how often the bore of a .22 rimfire rifle should be cleaned have differed. Anyone on my college rifle team who dared touch the bore of one of the Winchester Model 52s we shot risked being tarred and feathered prior to walking the plank. Some shooters still subscribe to that, but it has now become popular to clean, although in cautious moderation. If powder fouling remains in the bore of a carbon-steel barrel and the rifle is stored for a long time, it can attract moisture and cause pitting. A dry patch through the bore will whisk away most of the fouling, but for long-term storage, a light film of rust inhibitor should be applied.
The bores of target rifles that are fed nothing but ammunition with bullets coated with a soft, waxy lubricant are not as likely to rust. About every 250 rounds I push a dry patch through the bore to remove loose powder fouling, and the chamber leade is scrubbed with another patch. More serious cleaning waits until accuracy begins to drop off. The occasional flyer is often a better signal than an overall increase in group size.
When possible, bores should be cleaned from the chamber end of the barrel, and a cleaning rod guide should always be used. A pull-through cleaner, such as the BoreSnake from Hoppe’s, is commonly used in the Ruger 10/22 and other autoloaders. For removing light streaks of leading, I saturate a cotton patch with Kroil penetrating oil and push it through the bore. After allowing it to work for a few minutes, another patch wearing a coat of J-B Bore Bright is pushed with 30 to 50 complete strokes.
After the ring of carbon is softened by an application of Kroil treatment, it is scrubbed away with Bore Bright applied to a worn-out .22-caliber bronze brush. Push the brush in only as far as the chamber leade, pull it with short strokes and then withdraw the brush from the chamber. The brush will have to be bent about 30 degrees to reach through the ejection port of a 10/22. When cleaning a sporter with a rough bore, I substitute J-B Non-Imbedding Bore Cleaner for the Bore Bright.
The level of accuracy delivered by match ammunition is due to several things. One is the soft wax-based lubricant on bullets; Eley uses a beeswax-based lube. The coating of lubricant also minimizes leading. Cleaning the bore with powder solvent removes the lubricant, and while a few fouling shots will fully restore accuracy in some rifles, other rifles may require shooting an entire box of ammo.Finding the Right Load
Unlike competitors who develop handloads capable of delivering the best accuracy in centerfire rifles, those who compete with the .22 Long Rifle in the Olympics and other events have no choice but to first settle on a brand of ammunition and then seek out the manufacturer’s lot that delivers the best accuracy in their rifles. Once a lot is decided on, a supply of ammo for the upcoming competitive season is purchased.
As illustrated in the test results with Lapua Midas + in my custom 40X rifle, even the best match ammunition varies in velocity from lot to lot, and during accuracy testing at the factory, the average velocity of each lot is recorded. Some competitors have determined that their rifles deliver the best accuracy with a specific brand of ammunition at a certain velocity, so when placing an order for the upcoming season, they specify that velocity.
Trying different loads from various manufacturers is the option most of us follow. Then when that tack-driving load is discovered, we immediately rush back to the source and stock up on that lot number.