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Discussion Starter #1
Well, after a few range trips, with varying results, I wanted to know how good or accurate should I be with MBUS sights?

The first trip was in my parents backyard. 25 m standing freehand. I did alright, probably a ~6 in group. Also first time shooting the rifle. Using the large apperature.

2nd trip, to an indoor range, about 25 yds. Did very well, getting my last two groups with in a quarter. Again large apperature.

This is where it gets interesting. I go to an outdoor range, 100 yds. I shoot 20 rds. Aiming at center mass, I hit all 20 in the head (~6 in group) of the outline. Then I move the post down 2 clicks, just above center mass, 2 more clicks and we are good to go (4 clicks total). I was using the small apperature.

Then today, again in my parents back yard at 25 m, I was about 6 in low using the "25 m sighting target" and the large apperature.


I was using PMC 55 grain for all of these shoots. Spikes midlength upper with 1:7 twist chrome lined barrel.

I guess my real question is how accurate are the MBUS ? Also, should I use the large apperature out to 100 yds? I understand that they are back up sights and not fixed so obviously not going to be used for "match" shooting.
 

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this is a generalization but most sight posts on ar15 will be 7-12 moa @ 100 yards. depends on actually sight and distance from eyes.

so anything below that, IMO, is acceptable.

key is to know how to aim/shoot with them by practicing and then shoot accordingly when you need them.
 

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I was told that the MBUS sights were only for back up not primary use
 

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you should always use the small aperture when your trying to hit small objects. The large aperture is for low light and man size targets at very close range.
 

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My kid is better than me with them, but we can both usually hit an 8" steel plate at 200yds using the MBus rears, with a standard A2 style front sight. Also, definitely use the small aperature for anything over 25yds or so. My MBus is zeroed at 50yds with the small aperature.
 

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Discussion Starter #6
I was told that the MBUS sights were only for back up not primary use
They are, I just want to be comfortable and accurate with them before I get an optic.

My kid is better than me with them, but we can both usually hit an 8" steel plate at 200yds using the MBus rears, with a standard A2 style front sight. Also, definitely use the small aperature for anything over 25yds or so. My MBus is zeroed at 50yds with the small aperature.
Ok, I just realized this. I zeroed at 25m on a 300m target. So of course at 100 yds, I would be high (maybe not that high). I found a 25 yd/100yd zero target.
http://www.mcgeedigitalmedia.com/arfcom/100yardzerotarget.pdf

I think this might get me to where I want to be.
 

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my dad shot my ar when i first got it using a magpul mbus @ 25yds, 3 shots touching from the bench. depends how good the user..
 

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With a 300 yard zero you should be about 7 inches high at 100 so it sounds like you are right on the money. fyi after doing a many ballistics calculations I am a huge fan of the 50 yard zero. I'll post some info for you, from what I remember it keeps you within 3 inches all the way out to 270 yards before it start to drop significantly.
 

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With a 300 yard zero you should be about 7 inches high at 100 so it sounds like you are right on the money. fyi after doing a many ballistics calculations I am a huge fan of the 50 yard zero. I'll post some info for you, from what I remember it keeps you within 3 inches all the way out to 270 yards before it start to drop significantly.
I would be interested in finding more out about this.
 

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The reason a 50yd zero has become popular is that with the most common AR ammo, 55gr FMJ, a 50yd near zero has a far zero at 220yds and is never more than 2" from point of aim out to about 270yds. See this chart below for comparisons of some common zeros with M193

M193 25 meter, 50 yard and 100 yard zeros from 16" barrel





Likewise, if you zeroed your rifle so that the far zero was on at 200yds, the near zero would be a little over 55yds (sorry, no chart for that one, but just imagine it based on the 50 and 100yd zeroes above.)
 

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Discussion Starter #11
Thanks for the info Fdxpilot. I think I might try to work out a 50 yd zero. That seems to be the most versatile of the 3 on that chart.
 

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You might have some fun with this site. Nikon oriented but should work for any sights given the load and distances. It calculates variations in inches from one zero to another. You can find your bullet in the provided chart or enter your own parameters. Lots of fun to use and pretty true in practice.

Nikon Spot On&#153 Ballistic Match Technology Program
 

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Thanks for posting the chart. I forgot to sign back on yesterday and post the data I had on it. It really is a great zero. I never cared for the 300 battle zero.. 6 to 7 inches high at 100 just doesn't do it for me, or make much sense at all.
 

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Thanks for this Fdxpilot, going to have to site my gun in for 50 yards now.

And is this just for 55gr bullets? Or does it cover a few different weights?
 

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Thanks for this Fdxpilot, going to have to site my gun in for 50 yards now.

And is this just for 55gr bullets? Or does it cover a few different weights?
Obviously, the trajectory is going to depend on the Ballistic Coeficient (BC) of the round and the muzzle velocity, which varies with bullet weight and barrel length. Each individual round will be a little different. .223 55gr ammo will probably differ a little from the XM193 5.56 ammo in the chart I posted. There are many freeware ballistic calculators around that you can experiment with.

Just as an example, here is a chart showing XM193 55gr compared to M855 62gr military ammo, both zeroed at 50yds.

BTW - these charts are from a sticky thread on AR15 Zeroes and Trajectories at M4carbine.net

 

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Discussion Starter #17
Thanks for the reference, a lot of good info in that thread.
 
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