Now. Ain’t That an Interesting Development?

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.

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6 Comments

Filed under Firearms and their use

6 responses to “Now. Ain’t That an Interesting Development?

  1. Thomas Chumley

    Very interesting! Even though I hove no kind words at all for the Glock (any caliber, any model) I find the testing and the process very interesting. T.

    Date: Sat, 11 Apr 2015 20:45:12 +0000 To: tp_chumley@hotmail.com

  2. Hah! I am probably the only person in the known Universe ambivalent to Glock pistols. I neither loathe them or cannot live without them. They function well enough, but they have no ‘soul’.

    The main draw is my friend has several and that lends itself to comparison testing. You have figured out my ulterior purpose, of course. Barrel length doesn’t mean much until the change of length represents a significant percentage of the total.

  3. R M Datus

    A discerning polymath, as is Old Man Montgomery, might enjoy reading
    “An Empirical Study to Improve the Scientific Foundation of Forensic Firearm and Tool Mark Identification Utilizing Consecutively Manufactured Glock EBIS Barrels with the Same EBIS Pattern.” [https://www.ncjrs.gov/pdffiles1/nij/grants/244232.pdf ]

    A full understanding of the December, 2013, article will be most enlightening; however a few excepts include:
    “The research study was the first investigation to utilize multiple participants to examine fired bullets from consecutively manufactured Glock EBIS barrels with the same EBIS pattern in order to determine an error rate.
    Participants from 125 crime laboratories in 41 states, the District of Columbia, and four international crime laboratories participated in this study.

    Standard issue Glock barrels are polygonally rifled. EBIS barrels are essentially standard issue, polygonally rifled Glock barrels with an added manufacturing step. All Glock barrels are drilled, reamed, honed and cold hammer forged on a mandrel. The mandrel is a negative of the polygonal rifling profile. The cold hammer forging operation marks the end of the machining process for a standard issue Glock barrel. To create an EBIS barrel, a standard Glock polygonal barrel is further processed after the cold hammer forging operation. This additional machine imparts a barcode-like
    pattern on the surface of the lands within the interior of the barrel. The machine does this by inserting a rod outfitted with two carbide steel cutting wheels situated 180˚ from each other. The rod can make up to fifteen passes for a barrel with six lands and grooves. Each land can have up to five channels cut into its surface. Because there are two cutting wheels situated 180˚ from each other, opposite lands are imparted with the same barcode-like profile. Photograph 2 illustrates the EBIS pattern on two fired
    bullets. The barrels are placed on a holder to guarantee the start position and the rod is inserted from the chamber end. The rod tool with the cutting wheels remains stationary while the barrel turns. Channels are cut on the surface of opposite lands from chamber to muzzle as the barrel rotates around the tool following the rate of twist of the rifling. After one pass is made, the barrel rotates to a groove and the tool is extracted. The tool
    then positions itself for the next pass. According to Glock personnel, the tool does not go down the surface of a land perfectly straight during rotation, and they have no control of this action. Each barrel is inspected with a bore scope to ensure that the barcode pattern was imparted. The EBIS barcode pattern is imparted prior to hardening. Five hundred barrels can be imparted with an EBIS barcode pattern before the carbide steel cutting wheels have to be changed.

    Consecutively manufactured barrels represent the best possibility for the
    production of two firearms that could produce non-distinguishable markings since the same tools and machining processes are utilized back-to-back on one barrel after another. This process thus represents a situation where the most similarity should be seen between barrels. If there were ever any chance for duplication of individual marks, it would occur during the manufacture of consecutively manufactured barrels. The results of this
    research study, as well as past studies, indicate that sufficient empirical evidence exists to support the scientific foundation of firearm and tool mark identification. Once the specter of subclass influence is eliminated, each firearm/tool produces a signature of identification (striation/impression) that is unique to that firearm/tool. Through the examination of the individual striations/impressions, the tool mark signature can be positively identified to the firearm/tool that produced it.”

  4. R M Datus

    In “Ported Barrels: Practical for Police?” by Paul Scarlata, published in Police: The Law Enforcement Magazine Volume:25 Issue:9, September 2001, Pages:44 to 47, the article reported the results of tests on three ported pistols, S&W SW40P (.40 S&W), Glock G21C (.45 ACP), and Taurus PT957 (.357 SIG), to reduce the effects of recoil.

    The pistol is considered the epitome of handgun development: light, powerful, accurate, and capable of taking a great deal of physical abuse and still keep functioning. One of the shortcomings when it comes to shooting them is recoil. Laws of physics dictate that if a projectile of a certain mass is fired at a certain velocity from a handgun of a certain weight that a degree of reactive force—recoil—is produced. A great deal of time and effort has been devoted to limit the effects of recoil. One of the most practical is the ported barrel. In author concludes that ported barrels appear to provide increased recoil control and accuracy with only a slight decrease in bullet velocity.
    https://www.ncjrs.gov/app/publications/abstract.aspx?id=192468

    AGAIN, Old Man Mongomery’s strenuous testing procedures and protocols are verifying others earlier attempts at the same.

    • “Verification” is always reassuring. I’ve heard several arguments about the subject, all based on ‘seems to me’ and other rather subjective information.

      I have to admit, I did enjoy playing with the pistols.

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