Rem 550 I

[weaselfire]

The 550-1 has a floating chamber to accommodate short, long and long rifle rounds. It is tuned for long and long rifle so it should not give you issues, but a polish on the surfaces can help. The main cause of what the OP describes is often short cycling, and a bent, dirty or rusty main spring can be the cause. I have never seen an issue with Sears, or even sear springs, but replacing springs is not a dumb idea in an older, unknown gun.

I would start by cleaning and stretching the mainspring as well as a clean and polish of the firing pin and channel. Look at the feed mechanism for binds, clean and lube and check. Since it functions fine manually, I strongly suspect a short cycle condition.

Jeff

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[Rick Leslie]

Tony, also take a close look at the edges of the chamber. On a rimfire, years of dry firing (snapping on an empty chamber) will raise a bur on the chamber edge. This may be causing difficulty in chambering. I thought of this since you said the round stops before the rim reaches the firing pin. Like I said, everything is worth a look. I can tell you for sure that it will be the last thing you try that fixes it.