I just got a flyer from Midway, and they have the Leupold VXR Patrol 1.25-4x x20mm on sale for $369. Slightly over your budget, but it comes with rings and Picatinny base for an AR that you could sell or use on another rifle. The VXR Patrol has always been a $600 scope, I've never seen it for this cheap.
Another scope that sells for around $300 that I have experience with is the Primary Arms prism scope. (The poor man's ACOG). A stout tube and thicker glass make it a 1 lb. scope, but it is ruggedly constructed, and super bright and sharp. And there is a version that is calibrated specifically for the 7.62 x 39 round.
Adjustable diopter ( great for us guys with older eyes), tethered caps, the excellent ACSS reticle, lifetime warranty (great customer service from PA if you ever had problems, but I doubt you would).
It has a battery for lighting up the reticle red, but it's not needed, as the reticle is always there (a sharp black) whether it has a battery in it or not. I shoot mine 99% of the time without turning on the lit reticle. You could shoot this scope forever and never "need" the reticle lit up, but if you ever did, it's there.
https://www.primaryarms.com/primary-arms-1-6x24mm-sfp-scope-w-acss-300blk-7-62x39-reticle
As you probably already know, the x39 round isn't the flattest shooting one out there. With a 200 yard zero, it will drop around a foot at 300, and 3 1/2 feet at 400.
When I started using the PA scope, the ACSS made for the x39 round had me connecting first shot out to 400 yards. The reticle is calibrated spot on for the x39.
When you look at a pic of the reticle, it looks a bit "busy", but when you are actually looking through the scope, it doesn't look busy or cluttered at all.
Besides the holdover lines, there is a scale on the side for range estimation, walking target and wind leads. You can also estimate range using the width of the holdover bars.
The width of the holdover bars and the bars on the side scale correlate to the width of a man's shoulders at each range,18m inches, also about the same width as a deer's chest.
Don't just write off the ACSS after looking at the pic below, once you use it a bit, you'll gain a lot of new confidence with the looping x39 cartridge.
I put mine on an x39 AR, I prefer forward mounted red dots and scopes on my Mini-30's, but if I was going to mount over the action with the Mini-30's, I'd get another one of the PA prisms.
If you don't want a prism style scope and prefer a traditional scope, they also make a 1-6x with the x39 ACSS reticle.
This was a 400 yard test of 4 different loads, shot with the Palmetto AR and PA 3x scope. I didn't use the 400 yard holdover line, as I wanted to see the drop from a 200 yard zero.
Had I used the holdover line, I could have put them all on the aiming dot. You should be able to do even better with the bolt action Ruger than what is capable with the semi auto x39 carbines.
Note the fist size group at 400 with $7 a box Russian Silver Bear HP, it's the best Steel case load I've tried: