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i zer @ 50 yrds, high @ 100yrds, back to zero around 200?

Discussion in 'Black Rifle Forum' started by nickod, Oct 25, 2011.

  1. nickod

    nickod sammyb

    397
    0
    Oct 7, 2010
    my range only goes out to 100 yards. i zeroed @ 50 yards. its a little high at 100 yards (2-3").......so when am i back to my 50 yard zero? 200 yards? 300? ammo is always xm193, m855, or 75g tap. poa/poi seems to be almost he same with all 3 accoss the board. thank for the info guys.
     

  2. bmoore

    bmoore

    4,373
    5
    Jan 15, 2006
    Under a regime.
    Should only be around 1.5" high at 100 yards with a 50 yard zero I believe. That should get you back to zero at 225 yards.
     
    Last edited: Oct 25, 2011
  3. surf

    surf

    1,019
    4
    Jul 7, 2010
    As bmoore mentioned, ideally at 50 yards you are indeed around the 1.5" high at 100 and zero is roughly around 220 yards. This is why it is often referred to as the 50/200 zero but most people mistake this for being all in yards when it should read 50y/200m zero.

    I use the words like "ideally" or "roughly around" because in a non precision rifle that shoots around 2-3 MOA with say iron sight or a non-magnified optic, including shooter induced error and ballistic variance, there is that slight room for error. Now if it is a MOA shooting rifle with good glass, you will be more easily able to see the offsets.
     
    Last edited: Oct 25, 2011
  4. nickod

    nickod sammyb

    397
    0
    Oct 7, 2010
    very cool. so roughly ....no major hold overs out to 300 yards? or do i start dropping dramatically after that 220 yard mark?
     
  5. GSSF17

    GSSF17 ...2 of 'em

    1,280
    1
    Jan 25, 2009
    Central FL
    ...........all depends on bullet weight. Find one of the charts out there. It'll explain it all.
     
  6. surf

    surf

    1,019
    4
    Jul 7, 2010
    You will always have a more dramatic curve on the descending branch as opposed to the ascending branch of the trajectory, which I am sure you know. So if we are using "rough" estimations that will still maintain good "combat effective" types of hits, using a 50y/200m zero with your choices in ammo, you will be in the range of plus or minus 2.5" from contact distance out to around 250 yards. In reality your selection of ammo will be more like around 1.5" max ordinate at around 140-150 yards and will only be about 2" low at around 250 yards. Again these are "rough" estimates but will produce good hits on a torso if we hold upper center of mass.

    Here is a video where the rifle I am using is zero'd at 50 yards. Eotech, USGI trigger I engage steel targets at 220, 235, 265 and 450 yards. If you notice on the steel deer at 265 yards I am holding on the upper line of the back. I am taking heart shots so I am more forward on the deer. The 220 yard target is the dot in the center type of hold and for all intensive purposes on the 235 yard steel target is more or less a center hold, just slightly high. Now the 450 yard target I am holding off for not only drop but for wind correction also. FWIW I am using 55gr ammo which will have a slightly different trajectory than what you are using.

    http://www.youtube.com/watch?v=d8EH0AwYGsY

    Oh, btw here is a good read on zero's and some graphs.
    http://m4carbine.net/showthread.php?t=34671
     
    Last edited: Oct 25, 2011
  7. sounds about right so far. i was shooting 55gr fmj last time and i was zero'd at 50, 1.5-2" high at 100, 1" high at 200, 3" low at 300 and about 8" low at 400 iirc.

    need to redo this with my new 62gr loads.
     
  8. nickod

    nickod sammyb

    397
    0
    Oct 7, 2010
    Hey, m1a shooter, is there a rule of thumb like this for the .308 round? I need to know where to zero my new m1a scout with 155g tap. I'm assuming it won't be nearly as flat as 5.56. It's my first 308.
     
  9. surf

    surf

    1,019
    4
    Jul 7, 2010
    There are broad generalizations for all trajectories, however it really is as simple as going online and using any number of free ballistics calculators. Of course the more variables that you have the better off you are. There are several free downloadable calculators also and even Hornady has one.
     
  10. bmoore

    bmoore

    4,373
    5
    Jan 15, 2006
    Under a regime.
    I am a fan of the 50/200 zero for my coyote rifles. 223, 22-250 and 243. Maximum point blank range. You can pretty much put the crosshairs on them at 20 yards out to 250 and be within 1.8 inches of point of aim. Works well for predator hunting, sometimes its hard enought to stop them let alone figure out your hold over before they start moving again.
     
  11. the biggest reason for the double zero on a m4 is the height above the bore of the sights. or at least thats the way it was explained to me. with a m14, its not nearly as drastic as 50/200.