My cousin has a Browning Bar Type I (we think) in 300 Win Mag - It was failing to eject almost every other shot. He took it apart and cleaned it really well, put it back together. We shot about 7 rounds thinking it was fixed. Then it failed to eject again, the round got caught in the action on the way out. I started watching them eject. Some rounds ejected with moderate authority, some just lopped out and fell right beside the gun. He also had one failure to feed.

We're kind of scratching our heads at what it is. We suspect the gas system, but everything looks good and in good shape. When he took it apart to clean it, there was no buffer, so he ordered one and put it in and we thought it was resolved. Was going to try a new gasket but they are discontinued and sold out everywhere it looks like (if anyone has a lead on one let me know please).

Any ideas?

I'm not sure how similar the Type 1 is to the ShortTrac but you may also want to adjust the gas system. I did a full write up here on disassembly, reassembly, and tuning for running suppressed. I found that my rifle was way overgassed from the factory, even without the suppressor. There are two screws on the gas block, one is a lock screw and one is the actual adjustment screw. The lock screw has to be loosened prior to moving the adjustment screw! Read through the write up, it explains how to do it with pictures.

I also agree that any gas system parts should be clean and replaced if worn/damaged/missing. A full detail strip will allow you to clean everything up and hopefully get it running reliable again.

Check the extractor and ejector really well also. Make sure they are both moving correctly when pressure is applied against them.

If the magazine is deformed in the least it will interfere with the action bars and cause malfunctions similar to that

I had the same symptoms