.22 LR Accuracy Tip

.22 LR Accuracy Tip
Measuring the rim thickness of .22 LR ammo with a gauge like Hornady’s Rimfire Thickness Gauge and segregating the ammo by the same thickness is one technique for obtaining the best accuracy.

I enjoyed Layne Simpson’s article on .22 LR accuracy in the July issue. When I was around eight years old, my father taught me how to shoot with an old bolt-action, tube-magazine .22 rifle. I don’t remember the brand of the rifle, but my brother and I put countless rounds through it growing up. Here I am almost 75 and still shooting .22s and loving it.

For many years my brother and I have measured rimfire case thickness before shooting. We use the Hornady Rimfire Thickness Gauge and a digital micrometer to measure the thickness of the primer pocket of each round. There is always a significant variation in the measurements within most boxes of ammo because of the packaging methods of the ammunition. Multiple machines feed into the package-filling area, so the production variations between machines is reflected in the rounds in the boxes.


Why do we measure the rim thickness? Well, it has shown us that grouping rounds by rim thickness has significantly decreased the flyers in our groups. Some of what we thought might be wind variation turned out to be ammo related. I use small paper cups with the thickness measurement written on them. When I gauge a round, I drop it into that cup. It actually goes pretty quickly. After sorting them I place them into MTM plastic cases so that same-sized rounds are grouped for easy shooting.

I use several .22s for the shooting, including a customized heavy-barrel Ruger 10/22, a standard 10/22, and a new Ruger Mark IV Hunter pistol with a bull barrel. I have found that the brand of ammo has become less critical when the rounds are grouped by rim-thickness measurement. Some brands, such as Eley and Lapua, have much smaller variations in measurement, which may partially account for their better accuracy. My older brother began measuring his .22 LR competition ammo in college ROTC, and he has competed in iron sight matches at various meets up to and including Camp Perry using an Anschutz rifle.

Now we just enjoy being able to consistently hit our desired targets when we plink, as we did when we were kids. There are some old guys that can shoot really well!

Please keep up the good articles and remember that most of us started with .22s because it was the cheapest to shoot. It still is, just nowhere as cheap as it used to be!

Jeffrey Taylor; Greer, SC

Not So Fast

To Greg Lee of California who said in the July edition that Shooting Times should publish muzzle energy (ME) when comparing various cartridges because ME is the “one characteristic that defines a cartridge’s true power more than any other”: not so fast!

First, if you have muzzle velocity (MV), then you also have ME. Simply square the MV, divide the product by 450,400 then multiply by the bullet weight in grains.

As for the significance of ME, remember that lighter bullets slow down faster than heavier ones, and heavier bullets of the same shape have better ballistic coefficients.

For example, a .30-caliber 150-grain polymer-tipped bullet leaves the muzzle with 3,627 ft-lbs of energy, while the same bullet weighing 200 grains has an ME of 3,478 ft-lbs. But at 100 yards, they are essentially even (3,117 ft-lbs for the 150-grain bullet and 3,100 ft-lbs for the 200-grainer), and at 200 yards, the 200-grain bullet has pulled ahead with 2,765 ft-lbs to the 150-grain’s 2,681 ft-lbs.

Granted, there is not a world of difference, but it is not a good idea to judge on ME alone. The heavier 200-grain bullet would be a more powerful downrange choice for big game, but you would never know it by simply comparing ME.

John Fuquay; Cary, NC

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