Cool rifles. It's a junior weight/medium barrel 513 basically. I've had at one time 5 different 5XX rifles including an unfired 513. Last one left with me is a 511 - full size adult sporter repeater - with a about 1/2' diameter steel Weaver 4x scope and mount. I call it the "buck rogers" scope because of the teardrop shape of the adjustment covers.
Have fun with it!