I've had this carbine for about 4 years. It is an early carbine with a 200-range serial number.
When I first got it, it worked great with any magazine and any ammo, even the steel-case Brown Bear I had on hand. However. last year I had it out plinking and it was having trouble feeding and fully ejecting, even with good ammo. I though I had traced the issues to two problems: gummy old lube slowing down the bolt and looseness between the upper and lower.
I fully disassembled the rifle and cleaned everything. There was a gummines to everything due to attempted use of Frog Lube previously. I'm not specifically blaming the lube as in hindsight I know I didn't follow their directions (full strip, apply to hot metal sparingly). But any lube that fails so badly if instructions aren't followed exactly is a lube I will not use further.
While disassembled, I also noticed that the studs in the upper that hold the lower were a bit unscrewed, so I put them back in snug and reassembled. Much better fit.
Today was the first test since then and it was 100% successful. I used 4 mags that I grabbed: Glock-brand G26 10 round; Glock-brand G19 15 round; Magpul 17 round; the TNW "factory" mag, unmarked Korean 17-round. I like how the short G26 mag fits and barely hangs out...for range use. I went through 75 rounds of brass case Herters Select and 65 rounds of steel-case Brown Bear. Not a single feed, extraction or ejection issue! Was working beautifully!
I think my cheap, old Barska red-dot is trying to die. Even when "turned up to 11" (literally...the high setting is 11), I could barely see the red dot at 25 yards against the beige target paper with orange bull, even after putting in a fresh battery. It was also giveing me two distinct groups about 3 inches apart, so something inside may be shifting. Accuracy was good, though generally making a a single large hole about 2 inches across in each of the two groups.
Toward the end of the session, light was failing and it was easier to see the dot, so I put some rounds down to 100 yards. Was pretty easy to keep the rounds inside the scoring area of the target (even with the flared dot and assumed internal shift).
Glad my rifle is running well again. I need a better sight. And now I'm confident enough to order the conversion parts for 10mm!! Any and all comments are welcome.
Rob