Ballistics By the Inch — BBTI — is a website that does something we really like: tests and develops actual data about basic firearms facts. Like some of the other sites we’ve linked to over the last year-plus, it’s a myth-buster and a fact-finder. We do like that.
Some of these things have been extensively tested in the past, but three problems exist with these historical tests. First, the instrumentation available today tends to be more accurate than that available in the 20th or 19th Century, thanks to the computer and microprocessor revolution.
But the two other problems usually mean that those tests that do exist often are not on the net. One, perhaps they were done by government authorities that normally publicize data, but executed and recorded long before the internet’s event horizon of circa 1995. That means that they are only likely to be archived to the net if the agency cares enough to go back through its paper or microfiche archives and do so.
And two, perhaps they were done by some entity that did not care to put the information in the public sphere. Most foreign governments don’t, and companies conducting proprietary testing don’t.
BBTI’s Jim Kasper, Jim Downey and gang explain that these are only data points, and like any tests, BBTI’s have their bounds and constraints:
As we’ve noted previously, we have no illusions that our data is comprehensive. It is meant to be indicative – giving an indication to the general relationships between barrel length and velocity, or the effect of a cylinder gap. It would be impossible (for us, at least) to test all the different ammunition types available, or all the different firearms – particularly so when manufacturers of ammunition and firearms are constantly tweaking and improving their products. So use the data here to get an idea of what to expect, and perhaps as a jumping-off point for your own research.
Examples of the phenomena the site has examined include the effect of the cylinder-barrel gap on revolver velocity, the effect of shorter barrels on handgun velocities (starting with a long barrel and cutting it down), and comparisons of revolver velocities to equivalent-length, uninterrupted pistol barrels.
This is good data, it’s documented, it’s free, and it’s on the net. So what’s not to like? Well, apparently some people bitch about this or that. They bitch because he hasn’t tested Glocks (that’s coming). They bitch because they don’t understand the data. They bitch because… well, their psychologists could probably tell you. It’s data. It’s good. It’s free. What’s to bitch?
But with that said, we do have one quibble. In any aerodynamic or real-world ballistic experiment, you don’t have really comparable data unless you correct for atmospherics. This is usually done by correcting the data to an International Standard Atmosphere (ISA). The calculations are simple arithmetic, but you have to record the altitude, ambient pressure, and ambient temperature so that data can be normalized to an ISA (altitude Mean Sea Level, pressure 29.92 in/hg, temperature 59F). It’s possible they are doing this. This blog post, for instance, notes that they’re recording ambient temperature back in 2008. And this .pdf shows that they were thinking about pressure, but not pressure, when they originally conceived the tests. And there’s no question that they now how — Kasper’s a physicist, after all (and every drag racer figures this out — it’s not rocket surgery). It would be nice if they noted whether these are ISA value data, or provided us the ambient atmospherics so one of us readers could make the calcs.
But that’s our only quibble. Lots of information there, and more promised this spring.