Shoots high using the irons sights for me. Scratching my head.
Most Mosin's shoot high for some reason. But its a simple (no cost) fix that leaves the rifle "as-issued" and CMP GSM Rule compliant.
Mine shot 8 inches high when I got it.
To fix:
Measure the sight radius.
Note: Don't take these numbers as gospel. I did this years ago and I forgot the exact measurements but its close.
Divide the sight radius by 100 yards in inches
Lets say the sight radius is 21.6 inches.
There are 3600 inches in 100 yards ( 100 x 36 =3600)
Divide 21.6 by 3600 which will give you 0.006.
Therefore each .006 inch movement of the sight will move the impact 1 inch at 100 yards.
Again, my Mosin shot 8 inches high, so I need .006 X 8 to correct the sights.
8 X .006 = .048, meaning to zero my elevation at 100 yards I had to raise the front sight OR lower the rear sight .048".
The rear sight consist of a sight block that slides up and down the ladder, increasing or decreasing elevation.
There is one pin that you punch out that allows you to remove the rear sight.
Take the sight off and remove metal on the bottom of the sight.
In my case I needed to remove .048. So I stuck the sight in my milling machine and milled off .048 from the bottom. Put the sight back on the rifle and when the sight was set on the 100 mark I was on at 100 yards. I set it on 200, and was on, 300, same, all the way to 400 (I have gone be on that, 400 is the max of my range).
I used a milling machine, I file or stone can be used but care must be taken to keep it flat.
I don't know if the sight marks are yards, meters, or what ever the Russian common core math is, but the sights work with yards for me.
If you're off on windage, just drift the front sight left or right, depending on what you need. I made a sight drifting tool and use the above math to determine the drift. But trail and error works too.
Any way, you end up with an "as issued" rifle that shoots where its suppose to, and no gunsmithing bill.