It will make the video seem like it has more views, up until 301+, but it won't count as a view.
Whenever a video has less than 301 views on the video page itself, the number will increase anytime the page is loaded. It will lock at 301+. Then YouTube goes and looks at your views and only accepts what they consider to be views. They will basically deduct anything they don't consider to be a view. They only count one view from your IP address, so whether or not you refreshed your page 300 times, it will only count as 1 view.
Let's say you have a video that shows 301+ views, and you refreshed it 250 times. YouTube will only count 51 real views on the video. 50 form other people, and 1 from yourself. The video will be stuck at 301+ until you get 250 views from other people.
Once a video is passed 301, it does not update with every page refresh. It will update when YouTube audits the views, which seems to be random, and they will only take what they consider to be a real view.