With a rear sight set on "200" using a M91 or M91/30 how high or low from POA should the bullet hit at 25m or 50m?  Which is better to use for zero?

It's really impossible to say for sure, as it will depend largely on what ammo you're using. Also, they typically shoot high in relation to their rear sight setting. Between those two factors, it becomes anybody's guess. The best way to see is just to try it. I would use the 100m setting on the rear sight, though. All of the more modern "BSZ" methods will pretty much go out the window with these old guns.

My Finn 39 is dead nuts on at each range but I was asking about my new Finn 91.  Using 147 Russian ball it is high on the 200 setting at 50m by about 3".  There is no 100 setting so that is why I needed the 25 or 50m zero and where it should be with POI.  Guess it really does not matter, just shooting to have fun anyway.

If I had to take a SWAG at it, I would bet that it's pretty close at 200, then. Do you have access to a 200 yard/meter range?

my Russian 91/30 was hitting about 14-16" high at 100 yards with the rear sight at the lowest setting.

i just filed down an edge on the slider of the rear sight, you cant really tell. it brought the POI down to about 3" high at 100 yards.



i had an M44 that shot 2' feet high at 100 yards, and filed down a nail to replace the front sight post, then filed it to proper height while at the range, got that dead on.

in my experience, the Finn M27 rifle is the ONLY Mosin Nagant ive owned that shoots proper POI