Is the extractor broken?
That seems to be a common problem with the Winchester 100 and if that is the problem, it is an easy fix. I've bought a couple of Winchester 100s in 243 and 308 that the previous owners didn't feel were worth repairing and they either needed a good cleaning or the extractors were broken or both issues needed to be addressed, nothing more. The Winchester 100 is really a pretty simple action and if keep clean (and you don't break the extractor, they are pretty rugged and reliable.
I like Wincheser 100s better than the much more popular Remington 740/742/7400 series. I like the 243 version for coyote calling and I like the 308 carbine for still hunting whitetails in thick cover. The only version of the Winchester 100 that I've had serious issues with were those chambered in 284, as they were often very particular about the magazines, not so the 243s or 308s.
Jeff
