Ballistics By The Inch
A home brewed ballistics science project shows that size really does matter.
Columbia, MO – -(Ammoland.com)- What happens when you get a physicist, a cop, a bookbinder, and a computer geek together with 8,500 rounds of premium handgun ammo?
Only the biggest public database of how ballistic performance drops off over barrel length for 16 popular handgun calibers.
It started with a question that has fueled countless discussions over the years: does size matter? In this case, the question was posed by James Kasper to Jim Downey, about the optimal length for a self-defense handgun. And from that simple question, to which there are no simple answers, grew a research project. A research project that grew. And grew. And grew. Ending up with weeks of testing, a big pile of spent shell casings, and a website that has become a popular reference source for anyone interested in ballistics.
That website is Ballistics By The Inch, where you can find not only raw data, but charts and graphs, lots of documentation, and hints at the answer to the original question.
James and Jim eventually added in Steve Meyer and then Keith Kimball to their project, starting with thousands of rounds of handgun ammo and custom made 18″ barrels for a Thompson/Center Encore pistol. They established protocols for testing using two chronographs in which three shots of a given ammo for a given caliber were tested at 18″. Once all the ammo was tested at 18″, one inch of barrel was chopped off, and the tests repeated. And so on down to a stub of 2″ barrel.
The T/C was chosen to provide ‘ideal’ data, across cartridges which may traditionally be used in a revolver or a semi-auto handgun. This would help eliminate such factors as loss due to a revolver’s gap or the operation of a semi-auto ejector. But to make sure that the data collected was relevant, over 40 actual real world guns were also tested using the same ammunition, and those results included on the website.
One thing which is quickly evident from looking at the data is that the old ‘rule of thumb’ which says that handgun bullets gain about 50 feet per second for each additional inch of barrel length is woefully simplistic. For some calibers, the difference between a 2″ barrel and a 3″ barrel can be almost 400 fps, for others less than 50 fps. Some ammunition maxes out sooner than others in the same caliber. Some calibers continue to gain all the way out to 18″, others level out after only 6″, and some start to lose velocity at about 12″.
The four participants in the test have been pleasantly surprised at the response to their project. Initially launched at Thanksgiving 2008, the site quickly got a lot of attention around the world, and has been cited in discussion forums in at least seven languages. The recent revisions, which included a new round of tests (going from 13 to 16 calibers), has pushed the site to over a million hits. There has clearly been a real need for this information.
And that has been the most rewarding aspect of the whole project for the team members. Jim Kasper, who started it all with a simple question, and was willing to underwrite the bulk of the $20,000 cost of the project, figured that the data has probably been created before by gun and ammo manufacturers, but that the data had always been treated as proprietary. Now it is available free of charge for the average firearms enthusiast to comb through, consider, debate.
Ballistics By The Inch – Home brewed ballistics science that shows that size really does matter – but not necessarily in the ways that everyone has always thought.
James Downey is the bookbinder of the BBTI team, who has also been a gun owner and avid shooter for almost 40 years. For more information about all the members of the BBTI project, check out Ballisticsbytheinch.com/bios
Visit them online at Ballisticsbytheinch.com
View their Flicker page at www.flickr.com