A Remington 597 (22 rifle). After the first 10 rounds were OK, it started failing to feed and eject. Then, rounds would get stuck halfway down the magazine. Then, it got kinda fun when it started full-auto - 4 rounds with one trigger pull & the RO got a little pissed.
A buddy also bought one at the same time. His wouldn't fire a 10-rd. mag without malfunctioning.
After two factory "fixes" with nothing fixed, we both made Remington give us full refunds.