25 yard zero...

If I’m tying zero my Swiss rifles according to the rear sight (300 for G11 and K11, 100 for K31) how many inches above my POA should my rounds impact?

I apologize for this not being a straight answer to your question, but I do not think that trying to zero a rifle with open sights at 25 yards is a very good idea, UNLESS you use a target that is reduced in size AND know the trajectory of your ammo AND the height of the foresight blade above the barrel centre-line.

If, for instance, you take the standard ISSF target with an 8" black and set it up at 100 yds, then a 6 o'clock POA is in fact a sight line that is below dead centre of the target by an angle given by InversTangent 1/900 (4"= 1/3ft viewed at 300ft). If you move the same target back to 25 yds, then the angle is InversTangent 1/225 (4"= 1/3ft viewed at 75ft) i.e 4 times as much. And at 25 yds you need to take into account that the barrel centre line is about 1" below the sight line, so the effect is even stronger. In effect, the barrel is aiming much lower than you think.

If you want to fire a G11 at 100 you are going to need a higher foresight blade to get on target anyway. So to make it even roughly accurate, you need to know the exact height of the foresight above the barrel centre line AND the ballistics of your ammo. In addition, the sight picture of,say, an 8" black at 25 yds with a 6 o'clock hold, is different to that at 100 yds, and very different again to the sight picture at 300 meters (G11). This effect alone will cause a shift if you go straight from 25 to 300. So using a reduced target goes some way to ameliorating this effect.

And forgive me for asking, but why do you want to zero at 25yds at all? I have been there and I have done that - and with a G11 to boot. And my experience was that at 25 yds/meters you can't do much more than make a horizontal correction and check that the shots are in the black. About 1.5" above the POA is my estimate - but you will not be able to set it up to be dead on at 100, much less 300, unless you really, really know the trajectory of the ammo you are using. Which means knowing the actual muzzle velocity as well.

Yup. Patrick is right in there. The simple solution is to do it at 100 yards and we have the G11 front sight blade that will put you dead on at 100 yards. In fact we have all three, the G 11, the K 11 and the K 31. Just scroll down.

SHOP | Swissproductsusa

I recognize that 25 yards is not ideal, but it’s a known distance and the idea is to zero at 25 yards and verify at 300 (for the G1911 and K11) and 100 (for the K31). But I’m not looking to zero them all at 100, I want the zero to roughly correspond to the rear sight graduations.

I use the 25 meter or 50 meter zeroing in new rifles, where I have no real clue where they’ll hit.
Once I’m on paper at that distance, and normally you always are, I know if I can stretch immediately to 100 and do the real job.
It is just to prevent any discussions with RO ‘cause you’re shooting down the target stands or drilling someone else’s target...
I consider it a step one, a very short step, but still a step to take with new toys.
And works well.

Yeah Ovi if your dealing with an unknown or swapped a blade out 25 is a good start they have the 25 yard target on this site for the 303's but with hand loading it all but makes it superflous the only real measure is to do the hard yards and get the dope of the ranges you shoot by actually shooting them and even then its is a little hit and miss due to atmospherics time of day height above sea level etc etc.
But to give you a clue I concur with you Ovidio 25 yards to get you at least knowing where the rifles going I have seen so many guys try to zero without knowing where the rifles printing just give up because they are not even on the target!!!

That’s it. New and wholly unknown rifle. If I hit in the black at 25, then I’m safe to go at least 100.
Usually I hit paper also at 100 with new rifles, but I have seen a good pal of mine getting crazy, until we went to the pistol range and found out his Mosin was off by 4” at 25 meters. At 100 he didn’t even come close to his target.
Maybe the neighbour’s:D

My point exactly I have seen a guy years ago nearly wrap their 303 around the tail gate of their ute as after 10 rounds at a hundred meters zero hits! I remember shooting full bore I had a Sportco 308 coached at 900M 12 misses for a zero score I was well please when I got up from the mound so I know what it feels like to wash out with a rifle that you do not know where it is printing:ugh:

Might be completely different but I always zero my scoped rifles at 25 yards. Been doing it for 40+ years. Bullet is still rising at 25 yards so it will hit a bit high between 25 and 150 yards, be dead on at 150 and start dropping after that. For deer hunting it's a dead deer from 25 to 200 yards without altering the sight position After that you have to start aiming high. Fairly flat trajectory 243 although I've done the same with 300 Savage. Don't exactly need precision for deer, you have a 5 inch circle to hit, probably more. Then again, I rarely shoot a deer further than 75 yards away.

I do understand what you're intending to say, but for those who don't quite understand, no projectile can rise. At the point it leaves the muzzle it is dropping, indiscernible at first but unless it's rocket powered, it cannot rise.

Not sure what you are intending to say but projectiles do indeed rise. The barrels are aiming upwards to compensate for the trajectory of the bullet. They cross the same point twice. Depending on the caliber, 25 yards and 100-150 yards, the bullet will impact at the same point from level twice.

You fire a rifle with the barrel level, the bullet does drop immediately but as we are talking about normal shooting and sighting in, this is not relevant to the discussion.

It may be a matter of terminology for you, and the projectile will be fired up to reach a further range of course, but nothing rises of its own accord. No matter how high up you point that barrell, that projectile begins dropping upon firing.

We're definitely not on the same page. As you feel this is not relevant to the conversation, I leave it alone, but I would like you to think about what you just said. We'll agree to disagree.
The field is yours, sir.

Think we are just calling horses well horses here the only thing that does not suffer drop is a laser and they do have lasers that can knock things off however your both right A) The projectile does cross the line of sight twice as per illus and bullets do not rise of their own accord they are aimed up to compensate for trajectory.

But the original OP and a few posts that have been proffered it is feasible to sight in at 25 yards to see where its printing then step it out once you have L-R sorted the elevation can come at greater distances I use 25 for L-R getting it plum dead on as no variables that close besides if you say that at 25 yards you're within 1/4" is ok then at 1000yds then you'll be hitting 2 targets over from your assumed correct 25Yd zero, if not hitting in the next paddock.

Yup. When our type P/S 1000 yard Diopter system was proofed at Quantico, the first shot was at 25 yards.