High rise EOTECH accuracy loss in elevation?

[twinhairdryers]

I just received my most prized optic toy after much reading about the wonders of EOTech red dots. I mounted it on my flat top Carbon 15 M4 (Bushy) and it looks like everything I wanted in a very quick two eye acquisition red dot sight. I am wondering this...... I shoot a lot at the range for fun on paper, so slow fire at stationary targets is my hobby (cept for tacticle handgun different story).

My question is, I also have a decent Nikon Buckmaster 3-9X scope that is fun to shoot at 100-200yard range also, which is mounted on one of those good quality screw on aluminum riser mounts. I can take if off, put it back on and be within a couple clicks of zero every time. Very happy with this setup. Now, with the EOTech, will it hurt my 25, 50, 100 yard accuracy if I have it on the same type of aluminum screw on riser. IE, will I have to spend an hour to re-zero if I take it off? I know that the best setup for repeatability and accuracy is closest to the barell, on my flattop, but I like the changeability of optics more.

Anyone have any concrete idea on loss of accuracy if I add 3/4" to my sight plane on my red dot? It seems like I am loosing my elevation zero at different ranges - noticable say between shooting 20 yard target and then 50. I'm thinking it is due to this high mount system I'm trying to use. Anyone have any experience with this?

 

[RecoilRob]

Theoretically, if you could put the optics AROUND the barrel, both could be aligned dead on at a level, barrel height target. But, the bullet would begin to drop as soon as it left the barrel and so all shots would be low and getting lower as the range increased.

Mounting the sight plane ABOVE the barrel allows (or forces) the sight plane to be aligned with the same level target, but the barrel will be angled upward to hit it. This makes TWO ZEROS happen, one at close range as the bullet rises to the sight plane, then it goes above the LOS until it falls back down to the sight plane and you have your second zero.

The higher you raise the sights, the farther apart the two zero ranges will be and the more vertical dispersion you will have between them. Sorry, no way around it.

But, for the flat shooting 5.56, it isn't that much of a problem out to 300yds or so. This is assuming you are shooting at rather large targets. And, all dispersion will be vertical.

If you want to hit dimes at 25, 50 and 100yds, you will need to compensate because zeroing at 100 will make the 25 &50 hit low because the bullet is still rising to meet the distant zero. Same if you zero at 50. Will be low at 25 and then high, really high at 100. Just the way it works and nothing you can do about it but adjust your holds.