Jeremy S. recently reviewed the Mech Tech Carbine Conversion Unit for the GLOCK 20 and 21. This high-quality upper unit converts your handgun into a pistol-caliber carbine. While Jeremy’s test covered pretty much everything, he decided to send it to me to do a little ballistic testing, especially since I’d shown an unhealthy obsession with converting my GLOCK 21 into as many different guns as I could (previous installments included converting it to 10mm, and creating potentially the world’s only 9mm GLOCK 21.) So would I like to test converting it to a carbine rifle? Yes, yes I would . . .
To start off, let me just echo Jeremy’s findings — the Mech Tech CCU is a great item. It’s well-made, it performs excellently, and it does what it says it will on the box. The pistol lower snaps in quite securely, and it gives you the longer sight radius, attachment rails, and increased power that one would expect from a rifle version of a pistol.
This particular upper was chambered in 10mm. I used my .45 ACP GLOCK 21 lower with a 10mm GLOCK 20 magazine and it worked flawlessly. While I really liked it, if there is anything that I can say it’s missing, it’s that there’s no safety – which isn’t a fault of the upper, it’s a byproduct of using a gun lower that doesn’t have an inherent manually-engageable safety.
That point (to have or not have a manual safety) has been debated ad nauseum in the handgun world. Many people believe that a holstered handgun has no need for an additional safety. Be that as it may, a long gun is usually not holstered, and some sort of safety is usually found on all long guns. I think Jeremy’s suggestion (in the comments of his review) of using a MIC holster as a safety is eminently practical, and it’s the way I’d go when using the Mech Tech CCU.
I did some general chronograph testing for Jeremy’s article, and in addition, I wanted to see how the gel performance would differ from the 16″ barrel vs. the standard GLOCK 20’s 4.6″ barrel. I had tested CorBon’s 155-grain DPX in my prior video from the 4.6″ barrel, so I thought that would make a suitable candidate for testing from the long barrel. Additionally, I had a leftover Buffalo Bore 180-grain JHP from the chronograph testing, so I put that through a block of ClearBallistics synthetic gel while I was at it.
Now, most pistol caliber carbines in the common service calibers don’t usually see that much of a boost in velocity. According to the research done at Ballistics By The Inch and using CorBon DPX as the load for comparison, the differences are small. When using a .45 ACP rifle you can expect about a 127 feet-per-second increase for a DPX as compared to the normal pistol 5″ barrel (1229 fps vs. 1102 fps). For 9mm it’s basically a similar story; a 115-grain DPX travels at 1475 fps from a 16″ barrel, vs. 1315 fps from a 5″ barrel. Those gains are nice, sure, but they’re not tremendously different; they represent abput a 12% increase in velocity.
With 10mm, the story is a lot better; 10mm gains more from a longer barrel than the other service calibers do. I used my own chronograph readings for the DPX, and I also threw in a high-power Buffalo Bore round to see how it would do from the different barrel lengths. The 10mm gets a much bigger boost from the longer barrel; about 250 to 300 fps more for a gain of around 20 to 24% more velocity. Accordingly, the attendant energy increases are much higher too; with the DPX, the carbine delivered 44.84% more energy at the muzzle than the stock GLOCK 20 did, and with the Buffalo Bore it was a whopping 53.94% increase in energy (from 667 ft/lbs up to 1,027 ft/lbs).
That’s a lot of added power!
So then the question became – can we harness that power? Or will the ammo be overdriven and disintegrate? I put four rounds of DPX through a block of professional ballistics gel, 2 shots with denim and 2 shots bare (unfortunately, one of the bullets exited out of the side of the block and was lost). I then used the last Buffalo Bore bullet I had, sending it into a block of ClearBallistics synthetic ballistic gel.
From a distance of about 10 feet to the gel block, and with the velocity increases as noted, the answer is yeah, it was too much for the bullets to handle. The DPX bullets expanded and shed many of their petals; one bullet sheared off all six petals, one sheared off four, and one lost two. But the performance was quite good regardless – there was a massive expansion cavity, the initial damage tracks are huge, and the impressive thing was that the copper core of the DPX stayed fully intact so that even after shaving off some or all of the petals, we were still left with a quite large, reasonably heavy bullet that penetrated 20” or more. It wasn’t textbook perfect performance, but it was still very very good. The petals generally didn’t shear off until 8”+ in the gel block – so they stayed attached and contributed to the damage up to at least 8”, and some didn’t detach until 12” or further. That’s not bad at all.
The Buffalo Bore bullet was a more conventional jacketed hollowpoint over lead, and it fragmented all its petals in the initial damage cavity. The bullet started expanding right away and the force of impact just sheared the petals off right then and there. The result, interestingly enough, looked an awful lot like a G2 R.I.P. or a Liberty fragmenting bullet – an initial “starburst” of fragmentation, followed by a long thin trail of damage done by the core of the bullet. In the Buffalo Bore ammo’s case, that core was a smashed-flat bullet of commendable weight and size; it sent a 107-grain chunk of lead penetrating a full 14”+ while expanding to .583”; there’s nothing to complain about that!
However, I didn’t think either performance was really ideal; I think it’d be interesting to test a bullet that’s been engineered to perform properly at these velocities – that could be incredible. Or, consider something like a hardcast bullet (if hunting larger game or defending against larger predators); a hardcast 10mm would probably be an outstanding load at these velocities.
When talking about longer range though, both these bullets may actually be ideal performers. While those Buffalo Bore bullets were traveling 1600+ fps at the muzzle (and thus ripped themselves apart on impact), according to Buffalo Bore they’d slow down to about 1300 fps by the time they reached 75 yards. And that’s right at the sweet spot where the bullet performs best. So if you were using the carbine for targets at 75 to 100 yards away, the additional power would ensure that the bullet still had plenty of power to perform properly by the time it got there. So while these two types of ammo weren’t ideal performers at up-close ranges, they may very well excel at 75-100 yard targets. The carbine’s additional speed would ensure that the bullet was still fully performing at its ideal design velocity when it hit the target, and that’s a great thing.
Overall, I was quite impressed with the Mech Tech Carbine Conversion Unit, and it may represent my favorite iteration of the FrankenGLOCK phenomenon so far.