Will the 25m zeroing process work with an optic?

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Pops1085

New member
I've followed the basic 25 meter zeroing with my irons but I am going to put a RDS on and was wondering if I should do the same thing. And would it work with a scope too? I've heard about the 50 yard sight in also from some buddies who are a little more in the know, but I'd still appreciate some advice. Oh I guess I should mention this is for an Ar-15. :D
 
yes, the bullet still follows the same flight path whether you are using open sights or optics, the optics may rest slightly higher but generally speaking they should come out fairly close to each other.
 
All we have on base here is a 25M range, and guess how I zeroed my M4 with M68 before I left for Afghanistan?

Yep, 25M!

That being said, I never had to fire either of my issued weapons down range, despite convoy duty and other outside the wire activities. However, quite a few from my base have in the SFS arena and I've heard no complaints.
 
Here are the numbers for an AR15 .223 with a 1:7" twist, shooting Sierra's 69 gr JHPBT s@ 2800 fps...it's my target load when shooting the CMP Nat'l Match Course's shorter distances (200, & 300 yds). Obviously, I make sight changes for the varying ranges, but the trajectory remains the same out to 300 yds.

With issue iron sights and a non-removable handle-type of AR15...Colt Match Target to be exact. The + or - number is in inches above or below the sight picture, ie the top of the post front sight. I've used a 200 yd zero for illustrative purposes here. The numbers are from Sierra's CD "Infinity" ballistic and reloading data program and confirmed from actual match use. Issue sights on my Colt gun are 2.5" above the bore center line. For sighting in at 25 yds, with that Sierra 69 gr. bullet you'd adjust so as to have the impact point 1" below the top of the front sight post to get a dead on zero at 200 yds.
For a scope, low mounted on a rail, (no carry handle), you'd have to make adjustments beyond the following data.

BTW, the military round is several hundred fps faster than the load listed above and will flatten the trajectory somewhat from that listed below. I"ve estimated the current US military load at approx. 3200 fps....
HTH's Rod

Issued, iron sights 2.5" above bore center line, 69 gr. @ 2800 fps
25 yds = -1.0"
100 yds = +1.o"
150 yds = +1.5"
200 yds = zero
250 yds = -3.25"

With a scope attached to the top of the handle....(which add's an add'l inch to the height above bore axis...you get the following. Again, with the scope, and sighting in at 25 yds, you'd adjust so as to have an impact point 1.5" below the cross hairs to achieve a dead on 200 yd zero.

Scope attached to carry handle, approx. 3" above bore center line, 69 gr. @ 2800:
25 yds = -1.5"
50 yds = -1/4"
100 yds = +1.25"
150 yds = +1.4"
200 yds = Zero
250 yds = -3.1"

Issue sights 2.5" above bore center line, with Military load at ~3200 fps, same 200 yd zero.
25 yds = -1.3"
50 yds = -.4"
100 yds = +.8"
150 yds = +1.0
200 yds = Zero
250 yds = -2.3"
 
While a 25 yard zero is better than no sightin at all, there can be very small misalignments that will be hugely magnified at longer range. .25"@ 25 yards equals 2" @ 200. Maybe that's good enough, maybe not. I only use the very short range to verify if I'm going to be "on paper" at 100 yards(in case my boresighter isn't working).
 
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