I no longer live in California, so this lower is just sitting around collecting dust. It's made for a handy conversation piece, as I'm pretty sure I'm the only person in the State of Ohio who owns one.
It's time to let it go.
The lower was assembled by Sierra Sports in Modesto, California. I'm told he used a Bushmaster lower parts kit. It's been quite reliable. The first 100 rounds were problematic until the magazine wore in (common on FAB10's). Since then, it has faithfully fed almost exactly 500 rounds of XM193 and 500 rounds of Q3131A without a single hiccup. All total, there are approximately 1100 rounds through this receiver.
This is the earlier model, without the bolt catch. The earlier models had a hole in lieu of the bolt catch to allow the use of a plastic stripper clip guide. I still have the guide, but it's worn out. I'll send it if you'd really like. Otherwise, I might suggest modifying a USGI guide and welding a pin on the back to fit in the hole. It should work much nicer than the soft plastic guide sold by Shoeless Ventures.
The rear takedown pin includes a key ring to aid in breaking the rifle open. With practice, I was able to open the rifle, feed 10 rounds from a stripper clip, slam the rifle together, pop the pin back in, and chamber a round in 13 seconds, on average. My personal best is 9 seconds. With practice, I found the lack of a detachable magazine to be less cumbersome than I expected.
The finish is pretty good, with a few marks in the expected places where the upper and lower receivers met. There's one tiny ding on the right side, above the "FAB 10" marking. Not pictured are two scuff marks on the top of the buffer tube threads, which would be hidden by the upper reciever.
Since the stock is not included, I'll place the takedown pin detent and spring in a bag, along with the buffer retainer and spring.
I'm also including the DOJ approval letter, which comes with all new FAB10's. You'll want to keep this on you, as it once saved me from having my rifle temporarily confiscated by a well meaning officer who didn't know any better.
I'm asking $250, and that includes shipping to your FFL. You will need to make sure your FFL will accept a lower receiver from a private party. I will need an copy of his license, signed in ink before shipment for verification. The buyer will be responsible for the California DROS, transfer fees, etc.
Feel free to IM or email me with any questions. My contact information is available on request.