223 Zeroing questions

[SecuritySixShooter]

Ok so recently I purchased a Eotech 552 for my AR15. I purchased some Fiochi .223 to zero (Irons and Red Dot) on my friends farm. We were only able to zero at about 35-40 yards (guesstimate) at a 10 degree up angle (roughly). My question is what distance would I be zeroed for? If a 25 yrd zero is for 300 and 50 is for a 200yrd zero would 35-40 be around 250ish yards. That's my thinking IF I understand everything right. My second question would be if the slight up angle would affect the zero at all? As always any help would be appreciated.

SSS

 

[bang_bang]

My Marine friend told me a 36 yard zero should put you dead on at 300 yards.

He's an expert marksman, FWIW.

 

[KW]

Generally, 25-30m = 300m and 50m = 200m. That's fairly rough though. If you want to get exact, you really need to determine which ammo you are going to zero for, find out the ballistic coefficient of that round and muzzle velocity from your barrel. Then plug that into a ballistics calculator.

 

[rangerruck]

yes, the up angle will def effect you, with a short zero like that, becuase it has to climb that much higher, in such a short space, and you are not even zeroing with the irons. I would say, it was more like you doing a 20 yd zero.

 

[Al Thompson]

What are you zeroing for? If you plan for a HD sort of role, your probably set. For critters, I much prefer a 100y zero so I can place the bullet a bit closer to POA.

In any event, the only way to know where your bullets will hit is to actually put targets up at distance and shoot.

 

[hub]

+1 bang_bang.

This may help also.

chapter 9 Zeroing or specifically for range (9007. battle sight zero). pages 9-5, 9-6
http://www.scribd.com/doc/432351/USMC-MCRP-301A-Rifle-Marksmanship

 

[DMK]

I'm not a big fan of the 300m zero. With a 50y/200m zero, it shoots much flatter over a more usable range.

Look at the trajectory graphs on this page.

http://www.ar15.com/forums/topic.html?b=3&f=18&t=328143

 

[hub]

If possible I would zero the irons in at exactly 36yds. Being off by 1 or 2 yards will not give a true 300meter measurement. Then you can dial in your ranges with the rear adjustment knob.

As for the Eotech I would zero at 100 yards if possible. Your impact would be about .5 inches low 50 yards, dead on at 100 yards, and 3 inches low at 200yards and 10inches low at 300yards.

That's from a 55gr Sierra Gameking BTHP bullet at 3250fps. While other ammo would not be the same it would probably be pretty close.

I think that would just about cover the distances you would be accurately shooting with a red dot and is pretty easy to remember.