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Fire-4-Effect Glock Barrel Testing: Part 2, Unexpected Results

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In our current issue of RECOIL (#30) we featured some Glock barrel accuracy testing by Fire-4-Effect. If you haven't read Part 1 yet, we suggest you do so here before continuing. We'll Wait. You can also read the complete white paper here.

Okay, that didn't take too long. We'll summarize it a bit in case you cheated.

A Quick Rundown of Part 1
Fire-4-Effect constructed a custom barrel testing fixture in order to determine which aftermarket Glock barrel had the greatest accuracy potential. The fixture itself holds the barrel solidly in place in order to isolate the test to the barrels themselves as much as possible. Accuracy testing was performed at 20 yards with multiple aftermarket Glock barrels with three different types of 9mm ammunition: Atlanta Arms 115gr Match, Federal 147gr, and 115gr Remington UMC.

The barrel is secured in the rear of the fixture, and the front tensioning knob is to simulate it being inside a slide.

This all looks pretty good, but there was some disagreement among highly regarded engineers in the field about the efficacy of such a test. As a refresher:

Mark Hammond, VP of project engineering at Atlas Development Group, is an engineer who has been in firearms development since 2004, with nine of those years spent performing R&D for Remington. He had this to say:
“If you’re testing intrinsic accuracy of the barrel itself, what they’re doing does seem like a good way to isolate out exterior geometry. But as for exactly how it’s going to perform in the gun there are several other variables that contribute to accuracy.”

Hammond further stated, “What’s open to debate in my mind is what percentage of exterior dimensions affect accuracy since there is some slide movement [when fired] before the bullet exits. From an engineering perspective I would use a test like this to determine a desired type of rifling, but if I were really testing accuracy I would move toward testing the barrels in full-on firearms.”

Ethan Lessard, current VP of engineering at Q, longtime engineer with SIG SAUER, and former head of engineering at AAC, also had some input on the testing and fixture.

“The thing you care about is how the barrel changes accuracy in any way [relative to an OEM barrel]. If you want to find that out, you have to actually put it [the aftermarket barrel] in the gun.”

“Without seeing it disassembled and knowing exactly what knobs are turned down, I would say it looks far overconstrained. I can tell you for sure the barrel is not being constrained the same way that it would be in the gun.”

Lessard continued, “Your best shooting barrel out of this fixture could be your worst shooting barrel out of the gun. The way a pistol barrel is constrained in the gun when your gun is in battery is one thing; upon firing, when the bullet makes the jump to the rifling, the barrel, and slide will begin to move before the bullet exits … I’ve found that changing things on the outside of the barrel affected accuracy and precision far more than what was on the inside of the barrel, provided concentricity of the chamber and bore is consistent.”

As such our initial publishing of the results did not contain brand names because the jury was still out on exactly how definitive such a test would be. At least some of the statements by Hammond and Lessard were borne out.–if you check out our recent article entitled When Does the Pistol Slide Start to Move , you'll see that when filmed at high speed (50,924 frames per second in this case) many firearms, including Glocks, will have some slide movement before the projectile leaves the barrel.

After the first test using their custom built testing apparatus, the crew over at Fire-4-Effect told us about some additional testing they would be performing. True to their word, part two of the Glock aftermarket barrel testing was completed just about exactly when Issue 30 dropped.

As described in the first article, Part two of the 9mm Aftermarket Barrel Test did not use the contentious fixture. Instead Fire-4-Effect opted to use a Randsom Rest combined with a laser alignment device to ensure the same point of aim (POA) for every shot fired with each barrel. The Ransom Rest allows the barrels to be tested in an actual firearm, as opposed to a specialized fixture, while still maintaining the ability to be aimed and remotely fired.


Testing Procedure
The procedure for Part 2 remained consist with Part 1–outside variables were limited, the same very robust platform was used, with the same ammunition and the firing procedures.

The entirety of the testing protocol can be read here at Fire-4-Effect, but here's the Reader's Digest:

To summarize, each barrel was tested with the following steps:

The barrel is placed in the test firearm and secured per protocol in the Ransom Rest. Once secured and the range condition is safe for live fire, a single “spotter round” is fired using the UMC 115gr ammunition at the designated paper target backer, fixed 20 yards downrange from the barrel. With the spotter indicating the general area anticipated for POI, the laser-aiming device’s point of aim is marked on the target backer.

A clean target is mounted with the spotter round hole roughly centered behind it. A string of ten rounds is fired from the test barrel using the control (Atlanta Arms AMU) ammunition. The firearms’ POA is adjusted, if required, before every shot, until the laser projection is back in its designated circle. This replicates aligning the sights before shooting as an actual shooter would employ the firearm as well as this assures the barrel is theoretically being pointed at the same point in space each time. If the grouping is too large or contains characteristics of barrel movement in the fixture between string shots, the firearm is removed from the fixture, re-mounted per protocol, and the control ammo sequence is repeated on a new clean target.

If the barrel passed the grouping test with the control ammunition, the same shot sequences were performed with both the defensive (Federal 147-grain JHP) and practice (Remington UMC 115-grain FMJ).

Every round fired was chronographed and logged, and every group was measured for horizontal, vertical, and extreme spread using a Mitutoyo dial caliper.

The question on everyone's mind is this: Did the results from Part 1 of barrel test line up with Part 2? Let's have a look:

Some of the smallest cumulative average groups from the first best found themselves at the other end of the equation. Some decrease in accuracy isn't shocking when external variables are introduced. Exactly how much the grouping for each barrel would open up seemed more like the question (one of the KKM barrels only had a group open 10%, whereas the Glock OEM barrel got 300% fatter)–after all, one would assume that the match grade Atlanta Arms ammunition, the very same rounds used by the Army Marksmanship Unit, would bring the most consistent results.

Remember what they say about the word ‘assume', right? Check out the accuracy chart when Federal 147gr was tested:

Your eyes are not deceiving you. Almost entirely across the board, groups became smaller when using the Ransom Rest combined with Federal 147gr ammunition.


There are some more surprises in the data as well. For the full story and completely collated data, head on over to Fire-4-Effect's Proving Grounds.

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