Last month I completed three different AR platform lower receivers using the 80% Arms Easy Jig Gen 3 Multi-Platform 80% Lower Jig.
The Easy Jig is a great product, and provided much better results than I would have expected. It was also very simple to use, with easy to follow instructions and a process you’d have to work at to get wrong.
I had all the parts available to create and test the AR-15 platform, which is still running like a champ. But it took me a bit to find the parts necessary to complete the lower receiver and build an upper receiver for the AR10.
That ended up being a great opportunity. A long time friend of mine who owns Underground Tactical let me peruse the trash bin at the shop. Over the years, people have asked for their guns to be upgraded with better parts. Sometimes they want their old parts back, but usually not.
Well, one man’s trash is another man’s treasure. With just a few important exceptions, I built the entire AR10 using the recently completed 80% Arms 80% AR10 lower and leftover parts from other people’s guns.
First, it could have been a whole lot easier. Unlike the AR-15, there is no MIL-STD or “milspec” for the AR10 platform. They are built a lot of different ways, with several key component variations. Little things, like detents vs. screws in the lower small parts kit differ from one lower receiver to the next.
If I had been more patient, I would have simply ordered one of the lower small parts kits from 80% Arms. That would have given me everything I needed for this specific lower receiver. Instead of waiting, I chose to raccoon through small parts bins until I found each part I needed to fit the receiver.
In case you are wondering, it’s a DPMS pattern.
The receiver itself finished out just as well and just as fast as the AR-15. Just like the AR-15 version, the trigger pocket is a little wide. In this case, about 20 thousandths of an inch. That means that the trigger is going to wobble a wee bit inside the pocket until the spring arms are set into the little grooves on the pins.
Just to make sure it would fit, I pulled a CMC trigger out of the packing and installed it. It worked just fine. But in going with my “do it fast and do it cheap” goal for this build, I chose a binned mil-spec trigger. After a bit of polishing to smooth up the otherwise gritty trigger, it fit in just fine.
I found one small issue with the lower receiver during the assembly. The rear takedown detent pin pocket had not been completely drilled through. This pocket comes pre-drilled from 80% Arms, but it ends about 98% of the way down. That means the detent barely pokes down, and doesn’t fully retain the pin from walking back and forth once installed. A quick pass with a narrow bit and a hand drill fixed the problem.
With the lower receiver finished using literally thrown away and leftover parts, it was on to the upper.
Two parts that didn’t come from the trash were the 22″ 6.5 Creedmoor barrel and BCG. These were both Underground Tactical parts sitting on the shelf and are of the highest quality on the market. I went with an unfinished upper receiver from a model that Underground Tactical hadn’t made in years.
The whole process, including milling the receiver, took about two hours. The total cost, not including the jig, but including the cost of the 80% lower, would have been just a hair under $700, if I had purchased all of it online instead of finding most of it laying around the shop.
Once complete, the upper pinned right on the lower and it was time for finishing.
Which, of course, was backyard rattlecan.
Using Hornady’s 6.5 Creedmoor 140gr ELD Match ammunition, the gun shot just barely under 1 MOA five-round groups at 100 yards. With the handloads I make for a Ruger M77 Hawkeye Predator, it shoots just barely over 1 MOA five-round groups at 100 yards.
I initially poured some of the leftover vegetable oil from milling the receiver into the gun for lubricant, but after about 100 rounds it started to gum up a bit. I cleaned it all out with KANO Sili-Kroil and then added some CLP to the bore and BCG.
I’ve got about 300 rounds through the gun now. It’s running great and has taken an honored place in the pickup, replacing a hacked-up Mosin. Quite the upgrade.
Update: 80% Arms AR10 Lower Receiver Complete Build is written by Jon Wayne Taylor for www.thetruthaboutguns.com