Can a 300m battlesight setting be used with the A2 rear sight?
In other words, if you set the A2 drum to 300 and zero at 25m (like I learned to do on the A1, with POI at 25m being 1" below the aim point), will the drum settings for the other ranges be correct?
Yes.
No.
What barrel length, www? The latter question isn’t true with 16" or under.
As per US Army.
When zeroing a 20" M16A2 at 25m for a 300m battlesight zero.
Set the rear sight to the 3/8. The sight should be almost flush with the carrying handle, if there is a gap then crank it down and back to the 3/8. The difference is a 300m set and an 800m set.
Now click the sight one click forward (clockwise looking down on the rifle).
Zero at 25m, center on point of aim.
Click the sight back one click to 3/8 and your rifle should be zeroed for 300m.
With an M4 sight radius, do the same accept click twice or to the “z” marking on the knob that some rifles (Colt) have. Zero, click back to the 3/6, and you are good to go.
Well, I want to zero a 6.5 Grendel with a 16" barrel, so the whole issue might be moot.
I believe that last part should be:
With an M16A4 (20"), do the same except click twice from 6/3 or to the “z” marking on the knob that some rifles (Colt) have. Zero (at 25 meters), click twice back to 6/3, and you are good to go at 300 meters.
With the M4 14.5" barrel you leave the A4 elevation knob at 6/3 and zero at 25 meters and you are also zeroed at 300.
I don’t think so on both counts. In fact, I am 99% sure you are wrong.
And I have no idea how to zero a 6.5 grendel, I am only familiar with 5.56mm.
rifleman2000, take a look at page 3 of this PDF, it says the M4 is kept at 6/3 both for zeroing (at 25m) and battle (300m). The trajectory from the 14.5" barrel allows this so simplifies battle zeroing. As shown on page 1 the 20" M16A4 needs to be zeroed two clicks up then put back at 300m. Page 5 is interesting for the 50/200 True Zero.
http://www.usaac.army.mil/amu/ServiceRifle/M16-M4%20data.pdf
Interesting and thank you. Apparently, the Army has taught me wrong. I have saved that resource.
I too was surprised by this new information so saved the PDF for my records. Very informative and goes against what I was taught in the Army as well - but then I never qualified with a carbine.
I haven’t tried this with my new M4 yet as I’m waiting on a taller front sight post to play with the 50/200 True Zero as well. My barrel is 16" instead of 14.5 but that M4 data should work well enough for my needs.
Edit: WWW, I don’t have any info on the 6.5 Grendel either…
BTW, Molon, thank you Very Much for your extremely informative thread on the RIBZ (Revised Improved Battlesight Zero). I’m still studying it and want to modify my carry handle as you describe as soon as the taller Bushmaster sight post arrives.
So just to clarify for the slow kid: 14.5in barrel zero on 6/3, 16in barrel one click up from 6/3, and 20in barrel 2 clicks or at the “z” mark. Do I have this straight?
Awesome Wes-
Get the data for the round, bullet mass, muzzle velocity, BC, and such, find some online ballistics program and plot out different graphs and find one with crossover points where you want.
That make sense?
This is what I did with my 16" middy with an LMT rear. Reset the wheel so that it’s flush AND 8 clicks below 6/3, zero at 100, shot at 200,4 clicks up-300 at 6/3 and went to the 400, 500 and 600 with the dial up on the knob at the respective markings and she was smacking the 12x12 steel at all ranges. Where at, no clue, but in the grand sceem of things-does it matter?
No rest, just me and the rifle. If the steel was not bright yellow-you won’t see it at 600!
Mark
Where might one obtain copies of the targets? OR what size should the target be (I could easily zoom the copier)?
Yes, I know; one could easily create their own with a little geometry but I’m feelin lazy right now. 
Don’t get wrapped around the axle about target types. Get a sheet of copier paper (or some other light-colored background), and put a 2"x2" square on it, made of electrical tape, or pasties, or whatever.
Or, get black paper, rip a 3x5 card in half and attach it. Voila.
If you’re going for straight POA/POI, you have everything you need. If you are shooting to an offset in relation to POA, find out what it is and take a ruler with you when you shoot. Personally, I use my factory-original 3" booger-picking finger, divided into convenient 1" sections by the joints.
When we kick RCO packages for the Marines, we use a 1"x1" black or white pasty @ 36yd/33m, stuck to an E-silhouette/MRE box/illegal immigrant/whatever, for irons and optics. The smaller an aimpoint you can give yourself, and the more variables you can get rid of while zeroing, the better you are going to apply the fundamentals and get your popgun dialed in hard.
The targets that have the “how many clicks” graph on them are a nice training aid for remediation, but don’t really help a shooter figure out what they’re doing and vapor-lock it into the brainpan. Plus, you have to be really lucky to get an electronic file of a target in which the graph prints out to the dimensions they’re actually supposed to be. That generally does not happen.
Best I’ve seen so far are these. In Adobe Reader set Page Scaling to None to get the proper size on 8.5x11".
http://ohmr.ohio.gov/forms/ohmr2444-b.pdf M4 25 meter zeroing target
http://www.bobdbob.com/~deneb/doc/targets/m16a2-25m-zero.pdf M16A2 25 meter target
I’d say you’re about right there for 300m BZ using the 25m target. Honestly I don’t know if 16" needs the single click - I zeroed mine at 6/3 but I haven’t verified that at 300m and probably won’t until this spring. So darn cold and wet this last month plus my rifle range only goes to 200 yards. Gonna have to let that slide until next year. Impact is about right at 100 and 200 yards so I expect 300m to be about right.