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Ballistics by the Inch
Ballistics by the Inch (often called BBTI) is an ongoing project to test the performance characteristics of a variety of common handgun calibers/cartridges. The initial testing was done in 2008 and tested the velocity of 13 common handgun cartridges as it related to firearm barrel length. In 2009 an additional three calibers were tested and in 2010 and 2011 more calibers were added. Also in 2011 testing was carried out to study the "cylinder gap effect" on the velocity of ammunition shot from revolvers. All testing has been carried out as carefully as possible with no bias toward any particular manufacturer, caliber, or firearm. In November 2008 the BBTI website went online, describing the tests and making the data freely available so that anyone can dig out any particular bit of information they may be interested in. The website underwent a complete redesign in late 2011 with the addition of the 2011 tests.
==Barrel length tests==
The initial round of tests, and most later ones, tested handgun bullet velocity as it relates to the length of the barrel. The BBTI team wanted to test barrel lengths from 2 to 18 inches in one-inch increments. To have a consistent platform to test the various sizes and shapes of ammunition, a gunsmith was commissioned to create a custom barrel to fit each caliber tested. These barrels fit into a single housing, and can be swapped out easily, so the team can remove them for cutting. Each brand of ammunition in each caliber/cartridge was tested at 18". Then, the barrel was removed and 1" was cut off the end of the barrel and the cut end was dressed. Once all the cartridges had been tested at 18" and the barrels were cut and ready, each brand was tested again at 17" and so on, right down to a 2" barrel. Three rounds of each brand of ammunition were fired at each barrel length and the velocity of the bullet was recorded as it passed over two commercial chronographs 15 feet away. The resulting six numbers were averaged and the average plotted on a graph for each brand and caliber of ammunition so that the trend in the velocity could be readily seen. To date (2012) tests have been run on 21 different calibers/cartridges.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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