AR180B Gunsmithing; A Cautionary Tale

Good friend of the site Oscar sent me an upper that another gunsmith attempted to remove the barrel on. He got it back from said gunsmith with the message that he was unable to remove the barrel and afterwords he was unable to tighten the barrel back up.

What many do not know is that the AR180B has a unique method of barrel retention and it is not at all obvious.

If we look at a bare trunion you will note that it has a large hole through the middle with a small step.

The barrel for this gun uses an AR15 barrel extension that is turned down and press fit into this trunion. That’s it! Nothing else. Just a press fit.

What happens then when the unsuspecting gun plumber puts a barrel wrench on the barrel and clamps that flat sided receiver in his vise? It makes funny noises and turns the extension in the trunion. Not good. Oscar mentioned that it shot terrible after he got it back and I suggested he send it to me for inspection. It didn’t take long to figure out my initial thoughts were correct.

Now how do I fix it so it is safe to shoot? I want to thank Oscar for being patient with me as I have had his upper for quite some time while I try to figure out what to do.

I settled on a shallow pin. I wanted it to not show unless you were looking for it and still be able to hold everything secure.

Sneaking the Tig torch in between the bosses was challenging but ended up with good penetration after I got the amperage dialed in.

So what is the right way to remove a barrel for the 180 Bravo? Use a modified reaction wrench. Do not put any twisting force on the receiver itself.

New AR-180S Shorty Parts Have Arrived

I now have everything needed to offer shorty conversions or to sell the parts outright if you want to roll your own. CNC machined from billet steel these new hand guard caps will retain the cut down hand guards on an AR180 or 180B. Shoot me a message through the contact form if you need more details.

Very Early Costa Mesa AR-18 Pt3

Interesting things in this picture for sure. Lets start with what looks normal. the bolt, cam pin, firing pin and spring. That’s about it. Straight charging handle, shown here upside down. Similar to the AR180B but those are solid on the underside. Bolt carrier, a lightening cut out is full length as opposed to the partial cutout on the first 1000 Howa’s. Those were expected and had been seen before on other pictures like those of serial number X01. What wasn’t expected was the firing pin retainer. It has a split end not unlike the early solid version in the Colt 601.

A wider shot shows the guide rod assembly. These did not feature a latch as I believe it was found during testing that the rear plate would bounce when struck by the bolt carrier and unlock the upper from the lower. Not the kind of thing you want to happen in a fire fight.

What else do you see? Let me know in the comments and please share these articles with your friends.

Very Early Costa Mesa AR-18 Pt 2

Lets look at the more interesting side of AR-18 serial number 057.

There are early features everywhere over here!

Of course like the other side you see no reinforcement at the front of the mag well. The most obvious difference is the lack of a dust cover. Early testing showed that there was just too much space for dirt and debris to get into the action. This was fixed during later production.

No curved charging handle on these early models, just like the AR-16 that proceeded it. To my understanding the spent cases would sometimes hit the charging handle and bounce back into the ejection port. To remedy this they changed the design to act somewhat like a shell deflector.

Reminds me a lot of the AR180B.

Other features that may not be so obvious, the reinforcing ribs in the upper extend all the way to the rear. They stop short on regular production models.

Finally we move onto the lower receiver. Compare the front of the trigger guard to the one in your gun safe.

(What do you mean you don’t have one?) (Go get one.) (You know you want to.)

On regular production models the front of the trigger guard serves double duty as a guide for the rear of the magazine. Not so on this example.

Let me know what you see that is different. There is at least one more thing that can be seen in the above photo. Can you spot it?