Well, I finally had enough parts (and spare time) to put this thing together.
First Tip: Have the Right Tools to Do the Job!
Having all the tools to build an AR-15 is a good start but I also needed a different vise block than I normally use to hold the upper.
I'm not sure if it's the same for all 9mm AR uppers, but the Quarter Circle 10 upper receiver has different geometry than a regular AR-15 upper which makes it impossible to fit it into a clam shell style vise block like this one from Brownells.
Instead, a unit that holds the receiver by the takedown pin holes is needed. I borrowed this Odin Works unit from a buddy and I was off to the races.
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| Timing the Barrel Nut with the Upper Receiver in the Odin Works Vise Block |
Next Tip: Read the Instructions!
The ALG Defense EMR rails are my new favorite and, while I had to read the instructions through a few times, installing the barrel nut correctly was a breeze using their installation tool with its built-in indicator marks (as seen above). These marks help you properly time the barrel nut so that it's clocked in exactly the right position so that everything lines up when you install the rail. Admittedly, this is not the simplest system out there but the alignment was dead on after completing the procedure. The rail lined right up when I was finished.
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| ALG Defense EMR V0 Rail Installed and Properly Aligned |
Keeping it Simple
After installing the rail, all that was left to do to the upper was install the muzzle device and drop in the bolt assembly and charging handle. I went with the "Law Tactical Modified" bolt from Quarter Circle 10 in case I ever want to add a Law Tactical Folding Stock Adapter. Since this is a 9mm AR, there is no gas block or gas tube to mess with so the build is slightly more simple than a standard AR-15 build.
I decided to go with the HyperTap 9mm Muzzle Brake from Precision Armament. I have the 5.56 version of this muzzle brake installed on another AR and it performs very well. My expectations for this one are pretty high so let's hope I'm not disappointed.
Have the Right Tools: Part 2
After getting the upper put together, the next challenge was holding the lower in the vise for final assembly. They now make vise blocks specifically for 9mm but I don't own one. Instead, I took an old Korean Glock 19 mag that I no longer use and put it in my vise to hold the lower receiver. This is exactly how a lower receiver vise block works so I figured it was worth a shot. My idea worked and I was able to get the lower set up and assembled.
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| Old G19 Mag Converted to Vise Block |
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| Our QuarterCirlce10 Lower Sitting in our Improvised Vise Block |
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| If you'd prefer to buy a vise block, I found this unit on Amazon. |
Due to the proprietary nature of the Quarter Circle 10 lower, it came with a fair amount of the small parts already installed. I still needed to install takedown pins, trigger/hammer assembly, safety selector, grip, and (everyone's favorite) the buffer detent and spring.
Finally, with the help of our improvised vise block, I torqued down the castle nut and staked it into it's final position.
Castle Nut Torqued Into Place
Wrapping up
If you've ever built your own AR-15, then a build like this should pose no problems. All in all, everything is pretty straightforward and only requires a few AR9-specific tools to get the job done. We'll be following up with a range report after I get a chance to take this thing out and see how it runs.
