Ballistics testing
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 Ballistics Testing Equipment © Copyright: © Ian Moris The Shooting Centre |
The objective of ballistics testing is to optimize consistency of the pellet’s flight path to the point where hopefully all pellets will travel through the same point. Whilst it is often said that no shooter can shoot consistently at this level of accuracy, testing remains important component when attempting to achieve a consistent overall result. It becomes of particular importance in the “Olympic Final” where points are awarded in 1/10ths rather whole numbers. Contrary to poplar belief that the patterns created by a group pattern of pellets is random, experience has shown the particular batches form distinct shapes, often vertical or diagonal lines. Even with the highest quality pellets, when pellets that are not properly matched to the gun, group sizes can reach nearly 10mm. enough to cost half a point a shot!
5 shot groups using a Steyr LP10 from diferent batches of the same ammunition type, size, weight, and manufacturer
The Basics
There are many variables involved, the vast majority of which have to do with manufacturing tolerances and are beyond our control. However with a little care we can reduce the effect these have and even eliminate some.
Pellets are manufactured in batches, in general each batch is made on the same machine using the same cutting dies and from the same batch of lead. Metallurgists tell us that different batches of lead have different properties including density, malleability and even crystalline structure, these variables also change with age . Properties which use today by forensic detectives to identify bullet sources! Whilst all the above are beyond our control we must recognize that each batch will be different and when fired by the same gun, have different in-flight characteristics. What is in our control is when we find a patch the is optimum we secure enough stock to last until we can test again.
A second set of variables involves the manufacturing of the barrel and pellet size. Despite the highest quality of manufacturing barrel have tolerances (minor differences). Top quality pellets come in a variety of sizes; 4.48mm, 4.49mm, 4.50mm, 4.51mm. In general the manufacturers will test the weapon and try to determine which size most suits the barrel and indicate this on the test card. This figure doe not determine how sung a fit the pellet is when inserted into the barrel, but how it grips the riffling and in turn how much resistance the pellet receives when fired.. As a rule of thumb, if it is provided, is it probably best of accept this figure
The final pair of factors are pellet weight and velocity when fired. Pellets from different manufacturers differ is design and consequently differ in weight. Manufactures also designate pellets as rifle or pistol with rifle pellets being slight heavier. Pellets oar projected by a burst of high pressure air. The energy provided should be constant, and by in large on top quality weapons it is. Given this “fixed” amount of energy pellets of different weight will travel a different speeds with heavier ones being slower. This factor not only affect the speed at which the pellet travels through the air but also the speed at which it travels down the barrel which in turn determines the rate at which the pellet spins when in flight all be it marginally. The other side of this equation is that given two bullets of identical shape, flying at the same speed with the same rate of spin, but differing weights, the heavier one will be the more stable in flight.
Taking Control
Our objective is to determine which of the above variables are within out control and fine turn the overall system to make it more consistent.
There are two approaches to testing Batch Testing and Weapon Tuning
