I dislike scopes on my Mini-30s, as it weighs them down and changes the handling for the worse.
But I do throw a scope on when trying different loads to see what shoots the best.
Since I have Ultimak rails on all 3, any scope has to be a long eye relief model.
I've used this Nikon 2.5-8x LER on several Minis and my GSR.
You can take any Nikon, such as a P-223, go to their Spot On app, and calculate drop for the BDC for any cartridge or weight , including the 7.62 x 39.
Of course you still want to shoot to verify at those ranges.
For mounting over the action, some good optics (all with lifetime warranties) are the Primary Arms. They make conventional scopes like the 1-6x, and fixed power prism scopes like this 3x.
All can be had with a 7.62 x 39 version of the excellent ACSS reticle.
This is a 3x that I put on a Palmetto x39 AR. It had me connecting first shot all the way out to 500 yards. Not an easy feat considering how much the x39 drops past 200 yards.
For half of the weight of the PA scopes, and twice the price, there are the Leupold offerings like the VXR-Patrol.
Once I've found the load that a particular Mini likes, off comes the scope and the FastFire dot goes back on.
Being that targets shot with the x39 are on the larger side, deer, hogs, bad guys, etc., and the ranges are closer in, under 300 yards, I find a 2 or 3 MOA red dot is plenty precise enough, very quick to get into action, great in low light, and don't weigh the Mini down or affect it's good handling.
The Fastfires I use weigh less than 1 ounce and are the size of your thumb.
If I can hit a coffee can every time at 300 yards, I see no need to burden down and slow down my Mini by scoping it.
I sight for 200 yards, at 300 the bullet drops 1 foot. So for a target like the above I hold the dot at the top of the green circle.
Beyond 300 it gets difficult, the dot is getting too large, and drop at 400 is 36 to 40 inches. I could make things interesting at longer ranges, but for precision you'd need an optic like the Primary Arms I talked about above.
I've shot Whitetail in Montana river bottoms, and the Fastfires are all I've needed.