WHY WE ADVISE AGAINST THE USE OF AFTERMARKET BARRELS OR SLIDES
Prior to introducing our raceframes, we had sampled a large population of original Glock® slides & barrels, and found their tolerances to be what we expected, consistently tight dimensions. When we sampled the aftermarket barrels & slides commonly available, we found the disparity in tolerances alarming, to say the least. Below we’ve detailed one example of an aftermarket barrel that demonstrates what a user can expect to find on the aftermarket in the way of out of spec components, and sold as a “Drop In” fit barrel. |
In FIG 1 & 2, a premium aftermarket barrel, offered as a “drop in” fit, is compared to an original Glock® barrel. In FIG 1, an easily detectable visual cue indicating that it differs dimensionally from the original Glock® barrel, is the considerably larger surface area on the base or bottom of the front lug on the aftermarket barrel compared to the original glock barrel below it.
Assuming the rear angle cut on the lug bottom is identical, there is a problem with the length or height of that lug, as the flat area is noticeably larger, ie the lug is probably shorter to be showing that much additional area. In FIG 2, not only is the front lug longer by 19.4 thousandths (.0194”) on the bottom, the front lip edge is cut square, where the original Glock® barrel has an angled cut on that lip to match the angle on the ramped wall in the frame that it must clear as the barrel drops down during cycling. This was not an unique or anomalous barrel from that supplier – we sampled 11 barrels from this manufacturer, and this barrel was in the middle of the deviation range we logged.
You might not think 19 thousandths is a critical dimension (there are other dimensional deviations on those lugs), but this was the easiest one to capture & demonstrate with a camera. Considering the tapered cavity in that well formed by the ramped wall, the square cut edge on the aftermarket barrel’s front lug’s bottom front edge (the chin) means the aftermarket barrel’s effective length is actually some 10 – 15 thou longer still as the OAL on the Glock® barrel was measured at the sharp edge at the top of that angled lip, not the bottom edge.
Glock® angled that cut on the front lip to match the ramped wall’s angle to prevent contact with that ramped wall, as the barrel striking it, while dropping down during cycling, can cause a number of issues, from cycling failures to catastrophic failure of the lockblock, depending on how out of spec that front lug is. The aftermarket barrel’s square cut lip, by itself will cause cycling issues. A square cut front lip on an oversized lug will cause either the barrel’s lug or the lockblock bridge to shear.
On a polymer frame this might take some time to demonstrate itself as the polymer’s flex will soften the impact & the polymer’s elasticity will allow the lockblock to move some, but it is a stress the original Glock® lockblock was not intended to accept and that will eventually cause it to fail as well. It would not surprise me if a good number, if not all, of the failures reported on original Glock® lockblocks, were related to aftermarket barrel use. Users assume, if that barrel appears to run fine for a few hundred rounds, it must be fine, so, later on, when a failure does occur, they assume it must have been their Glock® that failed. |
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FIG 1
FIG 2
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Fig 3 shows a frame that was run with an aftermarket barrel similiar to the one pictured in FIGs 1 & 2, which caused the lockblock bridge to shear (for those unfamiliar, the bridge is identified below in FIG 5).
The strike / contact indentation caused where the square cut lip hammered against that ramped wall has been highlited. It wasn’t just the hammering from the barrel – the slide’s mass played some part as the slide’s momentum would act similar to a dead blow hammer, bearing on the barrel a 2nd time during cycling, because the barrel would not drop down deep enough into the well behind the ramped wall.
When the square cut lip on the barrel’s front lug hit that ramped wall during cycling, the rear of the front lug becomes wedged under the lip of the lockblock bridge at an odd angle to it’s normal contact angle, and the barrel becomes a combination crowbar/wedge torquing the bridge upward at the front edge, which because of the front edge’s minimal cross section, is it’s weak point. Again, the driving force on the “crowbar/wedge” is the mass & momentum first of the barrel, and 2nd of the slide’s mass & momentum with the rear side of the front lug becoming the wedge, trying to pry that bridge upward.
This is a force or load that was not allowed for in the Glock® design as it should not be occurring. Over time, something has to give: the physics axiom about “an irresistible force meeting an immovable object” holds true. That horizontal indentation in the ramped wall is approximately 35 thousandths deep – that gives some indication of the amount of force being applied and how much space the barrel’s lug lacked. It also gives some indication of the number of rounds this frame ran before failure, as that indentation did not appear after only one round. |
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FIG 3
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FIG 4 shows a CCF RaceFrame® operated with a stock Glock® barrel. Note there is no indication of any contact from the barrel’s front lug on the ramped wall.
The contrast between FIG 3 & FIG 4 should give a user strong pause before choosing to use an aftermarket barrel. |
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FIG 4
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The lockblock highlited in FIG 5 is the block in the frame pictured in FIG 3, that was run with the aftermarket barrel.
For those unfamiliar with the Glock® lock block, what is referred to as the bridge, is the portion that runs from one sidewall bridging to the other sidewall. In this particular picture, the front edge of the bridge has pivoted upward while the rear edge has moved down some. |
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FIG 5
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In addition to the dimensions shown in FIG 2, the height of the front lug on the aftermarket barrel was 8 thousandths shorter than the original Glock® barrel, which would partially account for that larger surface on the front lug’s base, but not all of it. That barrel was in the middle of the range of the other barrels in the population we sampled, some measuring up to 11 thousandths taller than a stock Glock® G22 barrel.
For any of the barrels from this batch we sampled from this particular manufacturer to be properly fitted, the gunsmith would have to be a talented machinist as well as a talented gunsmith. And what makes it more difficult for the average gunsmith, the Glock® lockup sequence is different than a 1911’s, so 1911 gunsmiths will not be familiar with what to look for. That barrel is sold by it’s manufacturer as a premium "drop in" barrel, and priced accordingly.
The Glock® was designed with loose tolerances, with the design goal of reliable functioning in a hostile environments – you can literally drop one in a bag of sand, pull it out and the majority of the time it will function. The downside to a pistol set up to loose tolerances is that performance is surrendered, mainly in the area of accuracy, which is one of the goals of the CCF RaceFrame®, among others
What is deceiving is that most aftermarket components, no matter how sloppy the dimensions, will appear to function fine in a polymer framed Glock®, even though those components are causing damage in the barrel lockup sequence. In spite of a polymer frame’s more forgiving nature, of a sloppy fit component, that damage is still occurring - destructive forces or loads are exactly that, destructive. Eventually that out of spec component will demonstrate itself in a failure of some sort.
If you are currently running an aftermarket barrel, whether in our frame or in a Glock®, pull it out and do a basic visual comparison of it next to an original Glock® barrel. You’ll be surprised at what you find. If you have a digital caliper, take some measurements especially in the length of the front lug as well as the height. And if you find a barrel oversized in the front lug’s length with a square cut lip, check the ramped wall on your frame for signs of contact.
We have prepared this FAQ, not to attack any individual aftermarket component manufacturer, but to try to alert customers what they will encounter with the use of aftermarket components if they are not extremely careful in confirming those components are to spec & properly fitted to their frame.
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