It's going to be a real uphill battle to find a rifle and scope for $500. Your best bet it to scour the classifieds and how one comes up. I'd suggest saving some more and getting something with better quality. The Ruger is a decently heavy contour, but nowhere near a bull barrel. What type of shooting will you be doing? If it's not long strings, the bull won't really do you too much good, IMO.
http://www.whittakerguns.com/product/savage-12-varmint-22-250-26in-blued-heavy-barrel-real-clean
The one posted above is a great buy. And, IME, if you call and talk to them...they will negotiate some on price. And when they say real clean, that means it's pretty much mint.
If it were me, I'd look into something similar to what I posted and save, beg, borrow, and/or barter a good piece of glass. Some real decent optics can be had for around $200.
In the long run, you will be more happy with a more quality rifle and optics combo. I've bought stuff in the past to save money...only to end up having to sell it or replace it. So, in the long run, no money was saved.
Look around the house. You will typically be surprised at how much stuff you may have to sell for some play money. And, if you are diligent enough, just tuck away $5 a day or something...that will add up very quickly and you'll be into the quality rig that you really want and deserve.