Here's the scenario:

Platform: Oly PCR-4  20"
Distance: 100yd and 200yd
Sights: Iron sights
Ammo: XM193
            IMI M193
            Black Hills SMK 69gr.


I started out at the 100yd range with XM193 and Israeli IMI M193. Both did well, IMI actually did better,1MOA.....XM193--1.5MOA.

Then moved to the 200yd target.
The same settings were kept: target aquisition and no change in sight adjustments.
Ammo used : SMK

However, I noticed that the 200yd SMK shot almost 8" higher than the 100yd XM193 or M193.
They were dead center except for the height.

Is this normal or a deviation due to different ammo usage?

different ammo loading will shoot to a different POI, especially at longer ranges.  You must sight in for the ammo you intend to use.

tagged

Quoted: However, I noticed that the 200yd SMK shot almost 8" higher than the 100yd XM193 or M193. They were dead center except for the height. Is this normal or a deviation due to different ammo usage?

Definately not normal - that is way too much difference.  You shouldn't see much more than 2" with a 100y zero.

What range did you zero at?

Forest,

This rifle was zeroed at 100yds.

It shoots well with M193, Q3131A, a tad wide with XM193 ....but is X ring dead-on accurate with BH 50gr and 60gr V-Max.

Oh yeah, fyi --- this is a 1:9 twist barrel.

I figured I would try some of these 69gr. SMK's for the longer distance shots since everybody seems to be having such good results from them.

The recoil explaination from the heavier bullet seems to make sense ( wouldn't take much of a rise in barrel angle to raise the target hit 8" at 200yds.) Or maybe I just need more practice--this rifle does shoot better than I do.

Quoted: This rifle was zeroed at 100yds.

If both rounds are hitting point of aim at 100y (which should be the case) the difference in point of impact at 200y is around 2".

The recoil explaination from the heavier bullet seems to make sense ( wouldn't take much of a rise in barrel angle to raise the target hit 8" at 200yds.)

If that were the case you'd see a significant difference in the point of impact at 100y.  Are you?

I'd follow that logic if were were talking significant differences in recoil (like going from a 55gr to a 200gr load).  But you are just increasing the projectile weight 14gr, heck I don't notice a difference when I switch to 75gr ammo (which is almost a 50% increase in projectile weight).

Or maybe I just need more practice--this rifle does shoot better than I do.

I'd go with this.  It may be you are trying to 'check your results' quickly after firing the shot.  (common with pistol shooters).