Lots of folks have built AR-15s and the YouTube library is full of videos on how to do it. (Okay, “assemble” for the purists.) I wanted to build an AR-10, so I could fend off bears, which looked like pretty much the same project, but with a larger caliber. I was hearing conflicting things about what would interchange in the way of parts, so I had a bit of trepidation.
Surprisingly, the first issue was magazines. The largest number of the AR-10 clones around use PMAG magazines, but the original Armalite AR-10 uses a magazine similar to that used in an M1A. These are not interchangeable, affect the mag well size, and any parts that attach to the mag well. One needs to make this decision on magazines before purchasing the lower receiver, as it will determine which receiver you want to buy. I was a bit biased toward the M1A style magazines, simply because I already owned a few, but it wasn’t a requirement.
I started by pricing some .308 lower receivers. They were over $400 at the time vs. AR-15 lower receivers costing about $90. I decided to wait. A year later the prices were $300. I decided to wait again. Then one day Palmetto State Armory (PSA) advertised blemished .308 lower receivers for less than $80. I bought one as fast as I could. Now I had the perfect Peoples Republic of New Jersey AR-10, a stripped lower! 😊
Putting one of these together requires a few tools and I bought a 10 round PMAG magazine so I could test whether it fit in the mag well. The PMAG .308 magazine fit the PSA lower. The M1A magazine did not, as expected. Next, I needed a lower vice block. This is nothing but a piece of plastic the right size to fit the mag well and hold the lower in a vice, while you attach parts. I already had one of these for an AR-15, but I needed one in the right size for the .308. I found a few online but they were ridiculous amounts of money for a plastic block. Finally, I ran across one for $10 on eBay, but it didn’t inform me whether it was for the PMAG type mag well, or the larger M1A type mag well. I decided for $10 it was worth the gamble and bought it. Fortunately, it was just what I needed.
Next, I needed lower parts. From just eyeballing the lower, it appeared that the forward end of the lower receiver was going to need larger parts than the AR-15, while it also appeared that everything from the mag well back was interchangeable with an AR-15. Meanwhile, the Peoples Republic of New Jersey won’t allow a collapsible stock, because collapsible stocks make the rifle so much more deadly. Don’t believe me? You haven’t met Loretta Weinberg have you? 😊
Loretta Weinberg, New Jersey’s answer to Diane Feinstein
I also realized that while the stocks looked the same as AR-15 stocks, the buffer and buffer spring had to be different. I finally decided to buy both an AR-10 lower parts kit, and an AR-15 lower parts kit, from PSA, so I could study what was different vs. what was the same. I figured I could always use the AR-15 parts later. I also found a .308 A2 stock kit on Amazon. I now had everything I needed to build my lower and I would have some AR-15 parts left over.
I started to put things together and quickly realized that buying blemished was a smart move. I could blame all the scratches I made on PSA! I put in the mag catch and tried putting in and releasing my one magazine over and over again. It worked! Next, I installed the bolt catch and a bunch of scratches. Without an upper it wasn’t clear if I could test this but it seemed to work. (Should I Cerakote the lower receiver pink to hide the scratches?)
Then I decided to move on to the pivot pin. The pivot pin was interesting, as it was wider than an AR-15 pivot pin because the mag well was wider, but the takedown pin was identical to the AR-15 takedown pin. It was also interesting because it did not want to install. The spring wanted to fly across the room, but not go into the pivot pin properly. I tried techniques from several different YouTube videos. Nothing worked.
I finally admitted defeat and took the lower and the pivot pin to the gunsmith and explained my problem. He tried it and sent the spring across the room. I thanked him for making me feel better, but the pin still wasn’t installed. Next, he took out some wire cutters and cut one turn off the spring. The whole thing went together perfectly. I sat there wondering why I didn’t think of that. I had to choose between my ego and having the pivot pin installed. Does that make me a “pin head”? ☹
Several more parts went in without issue. I ultimately needed to install the grip and found the curvature behind the grip was not the same as an AR-15. The result was any grip with a beavertail wouldn’t fit.
Fits
Does not fit
In addition, the grip is held on by a screw that goes up through the grip into the receiver. Again, it looked like the AR-15 grip screw, but I found some screws were a smidge too long and would interfere with the trigger, while others were fine. I realized an extra washer would fix the too long problem, having been through the pivot pin lesson, but I just used a screw that fit and left the too long screws for a future AR-15.
Will this fit?
I finally installed the stock, which went on fine, but then Murphy struck.
Orlando Shooting
Here I was with my finished .308 lower, with traditional A2 stock, NJ legal, and everything appearing to function properly, when a terrorist decided to attack a nightclub in Orlando, FL, resulting in the most deadly terrorist attack in the USA since 9/11/01. The resulting buying panic cleared the shelves of guns, gun parts, etc. including .308 upper receivers. Last I knew, a .308 lower wasn’t much use without a .308 upper. I was screwed. Murphy wins.
Nine months went by with PSA .308 uppers being “Temporarily Out of Stock”. Even if I was willing to gamble on someone else’s upper receiver fitting, none were available. Finally, I started to receive emails from PSA telling me that one particular .308 upper or another was in stock, but they would be sold out before I could sign on and place an order. It appeared I wasn’t the only one having the same problem.
After a month of frustration as emails came, and the uppers were always sold out, I signed on one day and the site let me place an order! Whoohoo! My upper receiver arrived less than a week later.
The Peoples Republic of New Jersey requires the muzzle device to be “pinned and welded” so you can’t change the device. Why? Ask Loretta. I hauled my upper down to the gunsmith and was informed that the device that came with the upper was a flash hider, which was not New Jersey compliant, and it needed to be replaced with a muzzle brake. One more purchase to make Loretta happy. The gunsmith turned around my upper promptly, and I now had my pinned and welded muzzle brake in place, instead of the chintzy bird cage flash hider that would have been fine by me.
Chintzy bird cage flash hider. No go in NJ!
Muzzle brake. Loretta thinks this causes the bullet to slow down. 😊
I went home and put the two receivers together for the first time. They fit! I added some MagPul folding Back Up Iron Sights (BUIS) (well plastic actually) and headed back to the range to sight in my new AR-10 clone. 😊 It worked! Don’t tell Loretta the sights fold!
Summary
Assembling an AR-10 clone is no more difficult than assembling an AR-15. However, a project which can be accomplished in a day took me about a year, due to the challenges of running down the correct parts in the middle of a buying panic, New Jersey compliance, etc. Would I do it again? Sure, it just took a long time, but everything went reasonably well and I am satisfied with the resulting rifle.
I’ll make the next one pink for Loretta! 😊
