I know this is old, but several people have these rifles, all are suffering from the same problem. Unfortunately, these rifles are made of poor quality. Follow these simple steps to correct your problems with both a sloppy, sticking bolt & a weak bolt stop.
1. Open the bolt and remove live round
2. Using a hacksaw / bandsaw, cut rifle into several pieces *.
3. Dispose of cut pieces in trash.
4. Purchase any rifle chambered in round you removed in step 1 (other than Remington brand)
5. Open bolt of replacement rifle and insert above live round.
This simple procedure will solve ALL of the problems you are probably experiencing with your 770.
* Purpose of cutting into pieces is to prevent uneducated person from retrieving rifle from trash, and ultimately suffering same disheartened results as you are.