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Zeroing my Bushmaster

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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: September/15/2005 at 21:07
paulosantos View Drop Down
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I am new to using rifle scopes, so I need lots of help.  I was in the Military and am a Police Officer in Nj and I have fired M-16's with Aimpoint.  I just purchased a Bushmaster Varminter Rifle and I am waiting for my Leupold MR/T 1.5X5 scope to come in. 

1.  I want to use this rifle from 10 yards to 400 yards.  Most companies tell you to zero your scope at 100 yards.  If I zero it at 100 yards, how will it shoot at 10-25 yards?  will it shoot high on the target?  I always thought it would be best to zero a Medium range scope at 25 yards so it could be used from close quarters to medium range (400 yards). 

2.  If I have my scope at 5 X magnification and I shoot at a target 300 yards out and the bullet hits center chest.  What happens if I set the magnification to 1.5 X magnification and aim for the same spot?  will it still hit the same spot?  Basically my question is if I change the magnification level will that also change the point of aim. 

I appreciate any help to my questions. 

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: September/16/2005 at 05:16
cheaptrick View Drop Down
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Welcome to the forum!

 

1) If you set your rifle up to zero @ 100 yards, you will be roughly 2"-3" high at 25 yards. Remember trajectory.

 

If you set your zero at 25 yards, you'll be back on at 225 yards.(Plus or minus)  

My AR's are set up with 25 yard zero's for CQB situations. Others use a 50 yard zero.

 

2) I don't know the answer there.

I would think there would be a POI shift due to the fact that the scope in question is a rear focal plane scope, and not a front focal plane scope.

The best way to prove or disprove that theory is to actually shoot at those ranges and see.

 

3) The best advise I can give you is to go to AR15.com and start going through the forums. There is literally more information about AR's there than you will ever need. Or maybe even want.



Edited by cheaptrick
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: September/16/2005 at 10:04
sandsock View Drop Down
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Another thing to consider is that for really close CQB, the rounds will impact lower at close range (under 25m) based on the optic (or even standard iron sights) being several inches above the bore (thanks to the line of sight).  Case in point, practice doing a failure drill aiming for a IPSC-size computer box (cerebral cortex).  Cheaptrick is on the money, going for a close zero will cut down the different in close but there will still be a small difference at ranges that approximate inside buildings (although if it's a full-size AR, it would be a bit less ideal than a shorty).  My advice is to go with a 25 or 50m zero, then practice drills at very close distances to become familiar with the weapon's characteristics.  The other question on POI shouldn't be much in my opinion with a quality scope (I had a Tasco "World Class" as a teenager that wandered diagonally between 3x and 9x) but I've seen a psychological difference on where the shooter has held their crosshairs at different magnifications which resulted in different POI

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: September/16/2005 at 19:04
paulosantos View Drop Down
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Thank you guys for the help.  I guess the easiest thing to do is just buy an ACOG scope and not worry about any of that stuff I was talking about, but I really like the Leopold MR/T 1.5X 5
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: September/18/2005 at 11:49
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What yardage you zero the rifle should ultimately depend on what range you expect to engage targets & the primary use of the weapon. Do you need the pin point accuracy to sever the nueromotor (not spelled right) strip or will a quick double tap into the torso suffice. If it will be used as a marksmans weapon I'd recommend zero at 100 yds and calibrate in / out in 25 yd increments. (Start a data book and record any adjustments you need to get inside a 1/2 of POA in 25yd increments from 25 yds to the max you will engage targets at.) Snipers Hide has an excellent format for a data book on their site.

If its going to be a CQB weapon go with 25 yds as a zero and adjust POI through hold over. Only time and expierence will tell you how high or low to adjust your POA.

 

Sorry I couldnt give you a straight yes or no for an answer but there isnt one. When you change ammo, heat, humidity, angle of the shot, sun position on the target all effect the POI of your round. These reasons are why a good detailed data book is a must for a marksman.

 

Joe

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: September/18/2005 at 13:20
paulosantos View Drop Down
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Thank you Joe.  I just checked Sniper's Hide, but was unable to locate the data book.  If you don't mind, can you reply with the web link?  I really appreciate all the help from everyone.

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: September/18/2005 at 15:26
cheaptrick View Drop Down
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http://groups.msn.com/TheMarylandAR15ShootersSite/zeroingmet hods.msnw

 

In addition to Joe's post, here's a good link that's been around a while.

 

Good luck!!

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