Vz 98/22 sight trouble

Hello, I have 2 Czech 98/22 rifles. These rifles have E stamps, meaning that they were accepted into Czech service, and were at some point sold to, I believe, Turkey. I say this because of a lack of foreign stamps on them.
The problem is that I can't hit anything with them, probably because of the rear sights, or perhaps because of the ammo that I'm firing.

1) The rear sights are marked in Arabic numerals, starting at 4 and going up to 21. A Turkish friend and I decided that these are most likely meters, though in the '20s and '30s the new minted Republic of Turkey was in a transitional period between their old imperial measurement system - in which case the sights would presumably be in Turkish Arshins (68cm) - and the metric system.
Using these 400-? sight, I hit at about 6" above my point of aim at 50 yds. I hit about a foot or so high at 100 yds. At 200 yds, I'm not even hitting paper; my rounds are hitting the berm probably 3-7 feet above, - and frequently wide of - my point of aim.
Why is this? What can I do about it? Can I get a different sight set to use with these rifles?

2) Could it be that I'm using the wrong ammo? I shoot a variety of surplus 8mm, but most of it is surplus light ball (~150gr) from various places. I know that in the interwar period, the German decided they wanted to switch to heavy ball ammo (~200gr). Could the Czechs have done the same? Would the Turks, or Persians, still have shot that?

I'd appreciate any help the community can give me.