the sliding scale on the factory sights is set up in meters. 100 meters is approx. 110 yards. That is why they shoot high.
Not quite:
A 150 grn. .311 bullet (7.62X54) will only be about 1/4 inch high at 100 yards when sighted in at 100 meters.
Mosins typically shoot 6-8 inches high at 100 yards. There have been many theories as to why. Some say they are made to shoot with the bayonet attached, some say Russians are taught to shoot at the belt buckle. Regardless, they shoot high.
You can put your bayonet on the rifle and see if that works but I don't think I'd mount a bayonet and attempt to fire a CMP GSM Vintage Military Rifle Match.
Personally, I like my sights to work on a rifle. I don't want to hold under 6-8 inches, yet I want my Mosin to remain "AS ISSUED" to meet CMP Vintage Rifle Rules.
My Mosin has a excellent barrel, but it shot "8" inches high at 100 yards. I did some calculations and determined that .0061 change in elevation would change the impact 1" at 100 yards or 1 MOA.
I took the rear sight off my rifle and milled .0488 off the bottom of the Slider ( thats the part that slides up and down raising or lowering the sight) so it would set .0488 lower on the rifle. (8 X .0061 = .0488).
I put the sight back on the rifle and found it would shoot POINT OF AIM on the NRA SR-1 100 yard reduced target when the target was set on the 100 marks, it also works when set on 200 at 200 yards, 300 @ 300 yards, etc etc.
(My range only goes to 400 yards, I assume it will work at other yard lines as well.
It's a simple process. There is a pin that holds the sight on the sight base. Push that pin out, and the rear sight comes off. You don't have to remove the slider from the sight. Turn it over and fill, mill, grind, the bottom of the slider to allow it to set down farther on the sight base (mine again was .0488). Just be careful to keep it flat and straight so it doesn't set cock eyed on the base. If you don't have access to a milling machine, take care is grinding or filing the sight so as not to take off too much. If you take off too much you can still use it, but your sight settings wont match the marks.
Then put the sight back on the rifle, when done, you can't tell any modifications was done by looking at the rifle. This does not impact the "as issued" status.