I have a friend who shall remain nameless. He’s a quiet, studious retiring sort. He doesn’t enjoy the limelight and public recognition. Which probably means he’s really in charge of a super-secret agency dealing with national security or aliens or something. Or not.
He collects Glock pistols. I’m not sure he has Glock knives, bayonets or entrenching tools, but he enjoys Glock pistols.
Just for the record, do NOT hold this against him. He’s really a good guy in spite of the Glock thing.
A couple weeks ago – I’ve been rather lax in this – we went out to the range and shot several of his Glocks using commercial loaded ammunition. What was interesting about this was he has an assortment of pistols and components, which allow for comparison of different barrel configurations, using the same frame and ammunition.
To be precise, we set up a chronograph and testing the following.
Essentially one Glock pistol, model 17 frame. This one frame employed the standard barrel of – according to the Glock website – 4.48 inches (or 114mm, if one prefers). A second barrel identical to the first, but with compensation ports. A third barrel with a threaded extention for a suppressor. (No. No suppressor available.) The third barrel is a bit longer than the standard barrel length. I seem to have lost the length of the threaded barrel, but it is longer than standard by about 5/8s of an inch. (Perhaps 3/4″ at the most.) (If not already noted, all these variations are chambered for the 9×19 cartridge, sometimes known as 9mm Luger or 9mm Parabellum.)
So. How do these barrel lengths affect velocity?
Not so much, really. We noted a discrete velocity difference, but rather minor in the grand scale of things.
Glock 17 using Standard Barrel, Ported Barrel and Slide (Standard Length) and Threaded Barrel.
Using Winchester ammunition identified as “Win USA9MM” (a 125 grain FMJ bullet as I recall), the Standard Barrel (Sta) gave an average of 1141 feet per second (fps). The Ported Barrel and Slide (Por) showed an average of 1126 fps. The Threaded Barrel (Thr) averaged 1157 fps.
So one sees a distinct difference in average velocities. But it isn’t much. The ported barrel is about 1.3 % slower than the standard barrel. The threaded barrel is about 1.4 % faster than the standard barrel. So the total variance between the slowest and fastest velocities is just over 3 %. The difference is actually less than the variation of any single barrel used in the testing.
To be specific, the standard barrel showed an extreme spread (which is jargon for the difference between the highest and lowest velocities recorded in the series) of 19 fps. Which by percentage of the average velocity is 1.7 %. So in reality, all these velocity readings overlap to some degree. The highest velocity recorded in the ‘slow’ barrel is faster than the lowest velocity recorded in the ‘fast’ barrel.
So perhaps all the arguing about ‘which’ barrel may or may not be ‘faster’ is probably not all that meaningful. Being afraid to use a slightly shorter barrel may not mean anything.
Here’s another ‘result’ from the same day’s chronograph testing. My friend who follows the discipline of St. Gaston also had a Glock 19. The Glock 19 has an official barrel length of 102mm or 4.01 inches. So it is about half an inch shorter. We tested it as well with the same ammunition.
The Glock 19 showed an average velocity of 1130 fps. Wow! That’s an 11 fps difference! Gangbusters! That’s less velocity difference than between the standard and ported barrels in the ‘full size’ pistol.
If anyone is worried about velocity loss due (only) to barrel length, quit. You now have one less issue about which to worry.
If one must worry, different pistols and revolvers do in fact differ. Not due only to barrel length, but due to variations in chamber size, actual bore diameter, cylinder gap and recoil spring strength. For reloader, burn rate of gunpowder may have some effect. But that’s another story. Or blog entry. Stay tuned.