I'm not very familiar with HK firearms, but this post hopefully won't be riddled with technical inaccuracy.
What would happen if you were to move your front-sight a few inches backwards? Would the difference cause a visual distortion of the sight picture/way the sights align? Reason I'm wondering is I have a Model 270 with HK's traditional style sights, but the front-sight has been moved a couple of inches backwards to make room for a suppressor.
It may be my eyes are acting up, but the sight picture appeared a little cramped with the 25m aperture. Basically it didn't seem wide enough to bracket the entire front-sight ring. Is that normal on the 25m setting? It is a bit of hack-job that's been done (typical UK Bubba-ing to plumb a suppressor on), so, the front-sight may be a little canted to the left.
I did once try an unmodified 270 and seem to remember the sight picture was slightly wider.
*Might be able to take a photo to illustrate what it looks like.