....why would you think it's stupid for a 16" carbine?
...the concept behind a 36YD zero is to decrease the "cone of fire" at distances up to 350YDS and allow a CM hold to obtain a higher percentage of disabling hits, which is the typical "effective" engagement range of a 16" 223/556 on "humanoid" objects. Remember, the typical issue M4 series is equipped with a 14.5" barrel, that's only shorter by approximately measuring from the tip of your forefinger to the 2nd knuckle.
The problem with close range zeros like the 25m or 36y zeros, is that these are really compromised zeros that were employed out of administrative conveniences. Yes they seem to offer (in theory) good ballistic solutions but in reality they don't work out as well as one would hope.
The problems that you'll run into are listed as follows...
1. Magnified optics (even LPVOs) tend to have parallax issues at said ranges, even small errors in zeros at these ranges become exagrated at employment ranges. I cant tell you how many times I've seen dudes conduct a close range zero and assume that they are good only to be bamboozeled at distance. 100y/m is the recommend distance for a reason, we are not talking about iron sights any more and that requires mindset shift. Yes PBZ's are still a thing and can easily be employed off a 100y/m zero but starting at 25/36 m/y and thinking your good is ignorant. Only exception is maybe a BDC reticle under certain situations.
2. Most "Humanoid" targeting concepts center around the idea of a full presentation. Now its hard to say exactly but this is actually pretty fucking rare in modern combatives baring CQC. Humans tend to move and seek cover/concealment in gun fights, especially at intermediate distances. The days of laying prone and cutting down Huns marching a cross wheat fields are gone. If you're lucky you might get heads and shoulders...maybe. So why the fuck would we employ a targeting concept like the 25m or 36y zero when that favors a sighting scenario thats not likely to occur?
You've done the math already and those targeting concepts are going to put your cone of fire high or even above the commonly presented target profiles and thats assuming your best application of the fundaments of marksmanship.
Bottom line is yes we want to stack the deck in our favor BUT given the technology and tactics at hand, 25m or 36y zeros leave a lot on the table.
Edit: Additional errors that occur with close range zeros is the actual range. Errors +/- a few yards or meters is not a big deal at 100 but closer in +/- a few starts to create error, its not horrible but it isn't great either.
