Late Sterling AR180 Headspace Issues

Had reader Scott contact me about his late Sterling AR180 that was sticking cases in the chamber and he determined that it was a headspace issue. He lives a couple hours away so he dropped by to have me set the barrel back. It wasn’t until I got the barrel removed that I found the real problem. It wasn’t a barrel set back issue at all like I originally thought. The problem was that the lugs in the trunion had worn out prematurely.

I suspect the heat treat was done incorrectly on the trunion as this gun showed signs that it had not been shot much or abused.

I know this is a sample size of one but could this explain why there were more Late, blued Sterlings built but the black ones are much more prevalent in the market today? Did many of those late Sterlings fail in a similar fashion? Has anyone seen similar problems in guns you have owned before?

For those that don’t know Sterling production went from serial number S15001-S27363 spanning the years 1979-1985 for a total of 12,362 rifles. I have determined that the switch from Black painted to Blued finish took place around serial S20000. That puts the mix at approximately 5000 black and 7300 blued.

7 Replies to “Late Sterling AR180 Headspace Issues”

  1. I have done a few of those over the years Rick. Only fix is a replacement barrel extension possibly from one of the part sets Numrich had long ago. As you know barrel clocking would be a crap shoot.


  3. Good candidate to fab up a .22 lr bolt and use a chamber adapter from a AR-15 conversion kit for a .22lr AR-180…

  4. About what range was the serial number on this weapon? That would be interesting to know. Thanks!

  5. Interesting. How do you get the barrel out? I was under the impression they were pressed into place like on an AK, but I don’t really know and I’m curious.

  6. Interesting.. Given that the lugs are cast into the trunnion, what options do you have? Seems like the only option would be to replace the trunnion with an 180B style one and press a receiver extension into it. No?

    1. I considered that but due to the way the trunion is forged in the original 180’s that is not possible. Replacing the trunion is possible but the finish would need to be re done. Finding a trunion would also be tough.

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