What zero for short range black rifles?

[gbran]

A lot of the black rifles have optics that set 2-3 inches above bore. My dad has a red dot on a PLR. The red dot sets 3" higher than the bore. He figures if he ever needs it for SD, he'll be firing at less than 25 yds, maybe a little more due to his big lot and desert behind him. He won't be target practicing at those short distances and only needs to hit COM's.

No matter where you zero the 5.56, starting with a 3 inch defecit, the round won't climb to line of sight in the distances he thinks it might need to perform.
BTW, my ballistics program won't allow me to do what-ifs less than 50 yards.

How do you experts deal with this issue and where do you zero?

 

[rino451]

It's almost irrelevant if he's using a red dot. Pick a distance, zero, and then figure out your come-ups/downs empirically.

with irons, I zero at 300m at 6/3 with 4 clicks of down available below 6/3, and then calculate my clicks & hold under for each range. Commit to memory (paper/cards).

There's volumes of info about zeroing (I assume an AR), and it's pretty much up to you. 0-2 aperture helps with the close range stuff with irons.

 

[rcmodel]

You should zero at the longest Point Blank range, which in the case of the .223 will be around 235 yards. Or 1 3/4" high at 100 yards.

That means you never have to hold over at any practical range out to 300+ yards.

You know the bore is 2 1/2" to 3" below the line of sight, so just hold 2 1/2" to 3" low at 5-25 yards.
Center of shirt pockets is about right!

Thats plenty close enough for GooberMint work!

rc.

 

[possum]

i zero at 50yds and that is because the poa/poi difference is only about 3 inches max from about 10 to 220 meters. which is plenty good enough for the ranges that i would be using the ar for. and additionally it is more conducive to not having to hold over or under at the medium ranges, you can really get away with putting the dot where you want the round to go and you got it. more realistically 10-20 feet is probably more like the ranges that i would be at if i had to use my ar for defense. at those close ranges you have to take into account offset. which with my ar and optic combo is about 2.5" low, therefore when training at those ranges i aim approx 2.5" high and i am on the money.

offset is very important and something many don't know about but it is important to know and understand.

 

[gbran]

Thank you all for the useful advise.

 

[W.E.G.]

The maximum point blank range for a 55-grain .223 bullet, with a muzzle velocity of 3100 fps, and optic mounted 2.75" above the bore is 318 yards if you zero for 50 yards.

With the 50-yard zero., you'll always be within less than 3" elevation dispersion anywhere in that 318-yard zone.

BTW, I didn't pull these numbers out of the ether.

See http://www.biggameinfo.com/BalCalc.aspx

 

[uvausmc]

You should zero at the longest Point Blank range, which in the case of the .223 will be around 235 yards. Or 1 3/4" high at 100 yards.

That means you never have to hold over at any practical range out to 300+ yards.

You know the bore is 2 1/2" to 3" below the line of sight, so just hold 2 1/2" to 3" low at 5-25 yards.
Center of shirt pockets is about right!

Thats plenty close enough for GooberMint work!

rc.

Remember that when are very close (5-25yds) the bore is 3" below the sight so you are going to need to aim HIGH, not low. Think about it as if the bullet is rising to meet the point of aim. When you are very close and you are zeroed for 300 yds you have to aim high so the point of impact will be where you want it.

When you zero for the max PBR this isn't as much of an issue unless you are aiming for a very small target.

 

[rcmodel]

so you are going to need to aim HIGH, not low.

I knew that!

Senior moment while typing I guess!

My advice still stands however.
Zero for maximum PBR, and hold 2 1/2" - 3" high at very close range.

Lets make it the first shirt button instead of the pockets!

rc

 

[DMK]

Remember that when are very close (5-25yds) the bore is 3" below the sight so you are going to need to aim HIGH, not low. Think about it as if the bullet is rising to meet the point of aim. When you are very close and you are zeroed for 300 yds you have to aim high so the point of impact will be where you want it.

I zero my AR15s at 50 yds, which works out to a 200m zero and about 1.5" high at 100yds. The AR has a sight line something like a 2.5" high over the barrel.

For very close range (15yds or less, I put the point of aim on my target (ie. the bullseye) at the center of my sight post (sighting as if I cut the top half off my sight post). This puts me right on target. With my Holosight/Eotech, I put my point of aim right between the bottom half of the circle and the pip in the center. At 25yds and out, sighting normally seems to get me close enough (within .5 to 1" of where I'm aiming).

You have to try it yourself, with your own rifle and sights or optics and at different ranges to get a feel for how you will need to shoot. I found my method by experimentation. It's easy to remember and repeatable. People look at you funny when you shoot a rifle at 15yds, but if you use one for home defence, you need to practice at practical self defense range.

 

[wally]

I like a 50 yard zero good all around compromise, especially if you don't have a range finder to actually know the target distance -- good practical zero from 25-300 yards for most common centerfire rifle calibers.

You need to aim high, not low at close ranges to compensate for the sight height.

On a humanoid target your critical region is about 18" high and 3-4" wide so no reason to obsess about elevation zero. Windage zero is a much more important factor!

This is why 2-liter bottles are in general my favorite practice target.

--wally.

 

[jester_s1]

What the "experts" do is zero for the longer shots and learn what the holdunder is for the shorter ones.