If we’re going to talk about accuracy, we have to use some easily understood means of comparing relative shot placement. Shot-group size is by far the most popular way to do this. Incidentally, the term “group” is correct; it is not a pattern. A pattern is the spread of shot from a shotgun; a group is the arrangement of shots from a gun that shoots just one projectile with each shot…. Dirt E. Harry
Archive for July, 2008
What should you expect? July 29, 2008
July 29, 2008A scope sight will make it easier to shoot any airgun more accurately, but it will not make the gun more accurate. Use a scope if it helps you shoot the gun the way you want to shoot, such as for long-range precision shooting and hunting, but also consider if other kinds of sights might even work better for what you are trying to do. For example, a red dot sight allows much faster target acquisition than a scope, but it isn’t as precise. If you don’t need that last half-inch of accuracy, it could be a good choice…. Dirt E. Harry
What should you expect? July 28, 2008
July 28, 2008The powerplant adds a small amount of additional potential, but that may become increasingly important with some kinds of powerplants if the shooter does not practice proper shooting techniques. Some powerplants, like those using compressed air, are very forgiving while others, namely spring guns, are not…. Dirt E. Harry
What should you expect? July 27, 2008
July 27, 2008Every product has specifications that limit performance. The barrel, powerplant and pellet are at the heart of every airgun’s accuracy. Other factors such as how controllable the trigger is and how well the stock fits the shooter are also important, but the barrel and pellet comprise about 90 percent of the accuracy potential for an airgun…. Dirt E. Harry
What should you expect? July 26, 2008
July 26, 2008Accuracy is always subjective. One person shoots at a tin can 20 feet away and another wants to hit an aspirin at 50 yards. Both consider their guns to be accurate if they can hit their target. Still other shooters want to see what an air rifle will do at 100 yards, while hunters usually just want a clean killing shot on their quarry. In this article, we will discover what you can expect from several types and even some specific models of airguns…. Dirt E. Harry
Airgun accuracy: July 23, 2008
July 23, 2008Next, is an article about AirGun Accuracy by Tom Gaylord who again is probably theee authority on air guns. Tom has forgotten more about air guns than most of us will ever know…. Dirt E. Harry
671 – the magic number: July 22, 2008
July 22, 2008The magic number is helpful when you have projectiles going near that velocity. For example, many big bore airguns shoot about that fast, so all you need in order to determine their energy is look at the weight of the projectile they shoot in grains. If someone tells you that his big bore .50-caliber rifle shoots a 180-grain lead ball at 700 f.p.s. and gets 500 foot-pounds of energy at the muzzle, you can now determine in your head that he is wrong. You may not be able to calculate the correct number in your head, but it’s going to be a lot closer to 180 foot-pounds than to 500 foot-pounds…. Dirt E. Harry
671 – the magic number: July 21, 2008
July 21, 2008A velocity of 671 f.p.s. for any projectile gives the same energy number in foot-pounds as the weight of the projectile in grains. For example, an 8-grain pellet traveling 671 f.p.s. generates 8 foot-pounds. A 20-grain projectile going 671 f.p.s. generates 20 foot-pounds and a million-grain (142.86 lbs.) projectile going 671 f.p.s. generates a million foot-pounds. A 3,000-lb. automobile going 671 f.p.s. generates 21 million foot-pounds, which is why we should be glad not too many cars ever go that fast…. Dirt E. Harry
Why care about muzzle energy? July 19, 2008
July 19, 2008You may not care, and it’s OK! However in many cases when you read an airgun specification you may see only muzzle energy indicated or only muzzle velocity. While for some people it’s irrelevant to some people it matters. For instance some country laws may prohibit ownership or import of air rifles above certain muzzle energy…. Dirt E. Harry
The formula for energy: July 18, 2008
July 18, 2008Multiply the product of the weight of the pellet (in grains) times the square of the velocity and divide that number by 450240. That last number is a constant created by multiplying two times the acceleration of gravity by 7,000 – the number of grains in a pound. The number I am using for the acceleration of gravity is 32.16 f.p.s. That number is obsolete, but the number that replaces it, 32.174 feet per second (f.p.s.) below the 50th latitude, does not change the energy calculation significantly.
Here’s how the formula works. Suppose we shoot an 8-grain pellet at 800 (f.p.s.). The energy would be 8 times the square of the number 800, which is 640,000. So, it’s 8 times 640,000 – which is 5,120,000. Now, divide that number by the constant 450240 and you get 11.371712. There may be even more digits out to the right of the decimal point, but that’s where my small calculator stops, so that’s my answer. I’m going to round off the number to two decimal places anyway, so I write it down as 11.37 foot-pounds. Don’t want to do the math?- just use the calculator at Pyramyd Air and skip the math altogether!…. Dirt E. Harry
