The model 77 wasn't one of Winchester's brighter moves but it should perform a lot better than that. First thing I'd do is take it down and clean it really well and then lubricate it with miimal oil and see if this cures it. If not you might see the problem in the process of taking it down and putting it back together.
Semiauto rimfires need frequent cleaning to keep the action working smoothly.
GB
Semiauto rimfires need frequent cleaning to keep the action working smoothly.
GB