July 22, 2016
By Layne Simpson
The accuracy-testing protocol for rifles has varied considerably through the years, not only among individual shooters, but also among the various types of shooting activities. It also is subject to being changed from time to time.
During the 1950s, National Rifle Association personnel often fired three-shot groups and allowed the barrel to cool down one minute between each shot. That protocol has since changed to five-shot groups with no barrel cooling between shots.
A friend of mine fires three-shot groups and allows the barrel to cool down two minutes between each shot. Another shoots five-shot groups and gives the barrel five minutes to cool between shots. The author of a test report I read several years ago fired five shots but measured only the closest three holes in the target for record. As I said, it varies.
Like most shooters, I have my own procedure for checking the accuracy of rifles. It remains the same regardless of whether the testing is done for my own information or for publication in an article. It is also the same for rifles owned by me as well as those received on consignment from the various manufacturers for evaluation.
This is not to say my methods are better than those used by others, and I am not implying that others should follow them. What I am saying is they have worked satisfactorily for me for several decades, and I see no reason for changing.
When testing a new rifle, I almost always start by shooting factory ammunition if it is available. I do this because factory technicians are quite good at developing loads capable of delivering levels of accuracy ranging from acceptable to excellent whenfired in a large number of mass-produced rifles from various manufacturers.
The level of accuracy may not be as good as I will eventually achieve through trial-and-error handloading for a specific rifle, but it gives me something to shoot for and to possibly improve on. If the cartridge a particular rifle is chambered for is available with match bullets, I try to shoot at least one of those loads. Due to excellent match loadings of the .308 Winchester from Black Hills and Federal, I love it when a rifle to be tested is chambered for that cartridge.
The Number of Shots
The rifle to be tested determines the number of shots to be fired in each group. If a big-game rifle immediately indicates the ability to average close to minute of angle, wear and tear on its barrel and the shooter are minimized by firing three shots and allowing the barrel to cool down between each group.
If a big-game rifle is capable of keeping three bullets close to or inside an inch at 100 yards, I could not care less about its five-shot accuracy. A custom Remington Model 700 in .338 Lapua I recently shot is a good example.
In contrast to that Model 700 is a recently tested 1940s-vintage Winchester 94 in .32 Special. Its first few groups at 100 yards exceeded 2 inches, so all subsequent groups fired by it contained five holes in the paper.
Varmint rifles and rifles used for competitive shooting are tested with five-shot groups. Back when I was into 3 Gun competition, some stages required emptying several AR-15 magazines. Target distances ranged from quite close to as far away as 300 yards, so when accuracy-testing a new rifle or load, 10 and sometimes 20 shots per group was the norm.
Regardless of the type of rifle or what it will be used for, I begin the program by shooting it over sandbags from a solid benchrest. The bench consists of a 4-inch-thick slab of reinforced concrete resting on concrete block pillars. It is about as steady as can be. (A small household throw rug placed atop the bench is easier on a gun's finish and the shooter's elbows than bare concrete.)
Rather than placing the chronograph atop the bench, I place it on a stool beside the one I am sitting on. Doing so makes it convenient to read, and the bench top shields it from muzzle blast.
The rifle is supported at the rear by either of two types of leather sandbags. If the shape of the cheekrest on a stock interferes with the taller ears of a rabbit-ear bag, an owl-ear bag is used. (The latter is also commonly described as a bunny-ear bag.) I have a couple of front rests and several styles of sandbags for them as well. The forearms of riflestocks vary considerably in shape and width, so a front bag matching a particular stock as closely as possible encourages consistency of hold and discourages canting of the rifle.
My Sinclair International front rest is set up with quick-switch tops holding bags of various sizes and shapes. The one I use most is called the Generation II AP Windage Top. Levers and side pressure plates allow the inside distance between the ears of its sandbag to be quickly adjusted in widths ranging in size from the narrow forearms of hunting rifles to those on varmint and target rifles measuring as wide as 3.5 inches. Switching tops takes only a bit longer than it took you to read this sentence.
Three other leather bags are used at the bench. The sausage-shaped bag measures 4 inches in diameter by 8 inches long, is filled with lead shot, and weighs 25 pounds. Used for soaking up the recoil of hard-kicking rifles, it is too thick to be placed between the shooter's shoulder and the butt of the rifle.
Rather, it lies on its side with one end resting firmly against the rifle butt. Resting the stock on a rear bag positions it higher than the top of the bench, so placing the sissy bag atop a sand-filled, flat bag (called a brick bag) elevates it to the desired level. Also for comfort, I rest my right elbow on a flat sandbag called a pillow bag. The various styles of leather bags I have mentioned are shown in the Sinclair International catalog.
If the rifle will be used in the field, it is further tested by shooting over the type of rest it will likely be shot over out in the boonies. A varmint rifle wearing a Harris folding bipod is an example. If the rifle is headed to Africa, it gets shot on paper from the standing position with its forearm resting on shooting sticks.
I have probably taken more of my North American game with rifles resting atop a daypack, so I make it a point to shoot a hunting rifle over one before heading for the woods. I have also taken game from the sitting position with my arm wrapped around a rifle sling in the "hasty" position. Shooting a rifle on paper the way it will likely be shot during a hunt reveals my accuracy with it in the field compared to shooting it from the bench.
It is best to accuracy-test a rifle during ideal range conditions with no wind, but since Mother Nature seldom cooperates where I shoot, wind flags are used. Sometimes described as wind indicators, an entire article could be written on their design and use, but I can touch only on the high points here.
Two flags placed downrange are positioned to allow me to see them in the field of view of the scope when its crosshairs are on the target. After everything is set up, I sit patiently and observe the flags long enough to spot a wind condition of fairly long duration that comes and goes more frequently than others.
Then when that condition comes around, I fire my shots into the target as quickly as possible. If the flags indicate a change in condition before all the rounds of a string are fired, I stop shooting and squeeze off the remaining shots in the group only when my chosen condition returns.
The correct placement of wind flags will vary among shooting ranges, but since most of my accuracy testing is done at the same range, I know exactly where they need to go there. Regardless of the distance, one flag is placed near the target.
One of the two Rick Graham flags I am now using has a larger vane than the other. I often shoot at 300 yards, and its size makes it easy to observe at distance. Tree lines border both sides of the private shooting range I use, and while the trees do a fairly good job of reducing wind velocity, their foliage is not dense enough to block the wind entirely. Wind is blocked even less after they shed their leaves during winter. Regardless of the time of year, the real trouble spot is a narrow gap in the left-side tree line at 215 yards. When shooting at 300 yards, the first flag is positioned in line with that opening.
The barrel is cooled down completely between groups. If the cartridge a rifle is chambered for is small and heats up the barrel slowly — e.g., the .22 Hornet — several groups are fired between barrel cooldowns.
The slow way of accomplishing this is to sit and twiddle thumbs until the barrel is no longer hot. Even when testing several rifles during the same session, a lot of time is wasted while waiting, especially during the heat of summer.
There are more important things in my life to be done, so a plastic bucket, a couple of plastic milk jugs full of water, and an insulated jug filled with ice cubes accompany me to the range. A rifle with a synthetic or metal stock and stainless-steel barrel can be held muzzle-down over the bucket and water poured down the outside of its barrel. This works especially well with an AR-15 wearing a handguard with openings over its entire surface.
While it should not be done with a gas-operated rifle, running water through the barrel is better because the cooling is more uniform from end to end. It is also the only way to water-cool a rifle with a wooden stock.
My homemade "barrel cooler" consists of a section of plastic tubing from the hardware store that measures 0.430 inch in diameter. It has a plastic funnel attached to one end and a cartridge case to the other. I actually have two — one with a .223 case for bores up to .35 caliber and another with a .308 case for larger calibers.
With a rifle held muzzle-down over the plastic bucket, the end of the tube is pushed into the chamber until it stops. Water is poured into the funnel slowly to avoid overflow back around the cartridge case. The barrel is immediately cooled down with absolutely no harm to it. Once the bucket becomes filled, the water is used repeatedly by dipping it out and into the funnel.
Shoot enough rounds and the water will eventually become hot, at which point it is cooled down with a few ice cubes or replaced entirely with cold water. After each cooling the bore is wiped dry by pushing through three cotton patches. One fouling shot is then fired, followed by shots for record. Regardless of whether water is poured on the outside or through the bore, in no way does it harm the barrel.
Like I said, everybody has a favorite procedure for accuracy-testing rifles. Now you know about everything there is to know about mine.