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Old August 15, 2008, 08:22 AM   #1
Beretta686
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10.5 A2 SBR Zero Range?

I just got a Bushmaster 10.5 inch A2 for my SBR and am wondering what range I should zero it in at.

On a 20-incher I use 25 meters, since it's one at 300m but with a 10.5 incher your losing lots of juice.

This is a plinker, so it's like I need it to hit 300 meter targets, but I wouldn't mind being able to reach out every now & then.
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Old August 15, 2008, 04:09 PM   #2
agtman
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On my LMT MRP 10.5", I went with the 50yd BZA using an Aimpoint red dot and 3x magnifier. That puts the bullet back on POA at 225yds (or 250yds, can't recall which).

With that zero, at least in theory, the 55gn 5.56mm projectile won't rise or fall below the line of sight more than 2.5"-3". That's definitely within minute-of-bad guy - or coyote - as far as point-blank range goes, and it's probably more range than a 10.5" gun can effectively use. Still, it's a practical zero and my 16" carbines are all zeroed that way too.

Remember: a 10.5" barrel on an AR means you're trading off a lot of muzzle velocity for ease of handling and portability. In turn that means you've reduced the projectile's fragmentation range and thus its effective terminal ballistics beyond a certain distance.

So although you might well hit something at 250yds (mine can hit steel plates all day at 300yds, no problem), whether the round will have any effective stopping capability is a different question.

See: http://www.bren-ten.com/agtman/id9.html



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Old August 15, 2008, 06:14 PM   #3
Zak Smith
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The problem with a 25-yard/meter zero is that at 100 yards, which is certainly a useful engagement distance for a rifle, the point of impact is about 6" higher than the point of aim.

Use a 40 or 50 yard zero with most ammo in a 10-12.5" SBR for a good PBR.

-z
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Old August 15, 2008, 09:24 PM   #4
AMX
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I used a 50 yard zero on my 10.3" M16. It just shoots so much flatter than the 25 meter or 100 yard zero's. No more aiming low or high, just aim at the target.

We had to put up with that 25 meter zero when I was in the Army. If it was a 25 or a 300 meter target you could aim at it but everything in between you had to aim low.
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