I picked up a lightly used Simmons Whitetail 4-12x40, I have had another in 50mm for a pneumatic air rifle for about 10 years, and they are really good IMHO, particularly for the $.
It's parrallax adjustable from 50ft to 100 yards which is useful, the finish is rugged and can handle the bush, and the general overall quality is high. Light transmission at dusk / dawn is very good, up there with other brands at 3 times the value. I have not seen a scope new under $300 for a while that comes even close. (Nikon / Vortex, on sale at the time!)
The only problem is, they stopped this line of scope a while ago, but look around, some places still have them new, but most are previously owned.
Good luck with finding a scope, a good one makes the Ruger real fun.
Candocad.