Look at what they go for new, which means including manufacturer's warranty, and then wonder what you are offering the buyer that makes it a better idea than a new one. There has to be some discount. The rifle alone, if I wanted one and had the money I wouldn't expect to pay less than 70% of retail for one that close to new condition but as it gets closer to new retail price a fellow thinks more towards paying the full retail for new with warranty.
The extras you describe with it are worth something, but anyone can get those as they need them, so they aren't going to give as close to new price for those as they will for the rifle.