angled rail questions

Discussion in 'Long Range Scopes and Other Optics' started by Long*range*Lapua, Dec 13, 2010.

  1. Long*range*Lapua

    Long*range*Lapua Member

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    I have got a few questions about replacing my standard taper rail with a 20moa rail.

    My problem: I recently built what i am hoping is a good medium to long range rifle. I started with a BAT 10inch action and 32inch lilja barrel. Rifle is chambered in 338 Lapua Imp. 40deg. I am shooting 300grn SMK at about 2900fps. I ordered a BAT rail for the action and a Nightforce NXS 12x42x56 with the CH-1 reticle. Everything works great except I run out of verticle adjustment at around 960yrds. Would a 20moa rail cure this? Currently I use Sierra Infinity in order to create a chart in order to click for distance. I would like to continue this but am unsure how having an angled rail would work. Any info would be appreciated.

    Nick
     
  2. BountyHunter

    BountyHunter Writers Guild

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    The NXS 12-42 only has 65 MOA of elevation to begin with, which is not a lot for LR rig.

    the real question is how much elevation do you have left when you are zero'd? You must know that first before you make any decisions.

    Lets say your setup puts you exactly in the middle of the elevation range and have exactly 32.5 MOA up left, that means you could run with a 30 MOA base.

    That would leave you 2.5 MOA left down from your zero.

    You are going to need a tapered rail of some degree, the question is how much. But you can figure it out as above.

    BH
     

  3. Long*range*Lapua

    Long*range*Lapua Member

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    I am currently zerod a 100yrds with approx 25moa of verticle adjustment left. 12x42 only has 45moa adjustment.
     
  4. RDM416

    RDM416 Well-Known Member

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    A 20 MOA rail should do the trick for you. If you have 25 moa of adjustment left with your 100 yard zero, that would indicate your scope is set at 20 moa from the bottom at 100 yards. A 20 moa rail would put you at the very bottom of the adjustment at 100 leaving the full 45 moa available for you to dial up..... that will get you well past 1000.

    At worst, you could end up not quite being able to get the scope to go all the way to zero at 100. That is really not a problem even if you have to do a 150 or 200 yard zero. That will put you 2" or less high at 100. Unless you are trying to make precision shots on very small critters at less than your zero range that should not be a problem:rolleyes:

    You might check out the 300 grain Bergers as well, the higher BC should get you to 1000 with no changes to your setup. I am shooting the Bergers out of one of my rifles at 2875. With a 100 yard zero my dial up for 1000 yards is 22 3/4 moa. External ballistics does not change from one rifle to another, so if you run the Berger at 2900 you should be able to get on target at 1000 with around 22 1/4 to 22 1/2 moa. Your current set up is giving you 25 moa of adjustment so the Bergers should get you there........ but not much further.
     
  5. dirtball

    dirtball Well-Known Member

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    Long*range*Lapua
    With the 12 x 42 NXS if you try to go to a 30 MOA base you will bottom out about 8 to 12" high at 100 yds.
    If you stay with the 12 x 42 your best option will be a 20 moa base which will be VERY close to bottom at 100 yds, you may have to settle for being a little high at 100 or set your zero at 200 yds. But it will give you 40 to 45 moa of vertical from your zero, which should get you out to 1300 to 1400 yds.
    When I built my 338 LM Imp, I used an 8X32 NXS which has 65 MOA of adjustment and a 30 MOA base and I ended up about 3 MOA from the bottom with my 100 yd zero and about 60 MOA of vertical adjustment, not that I will ever need it.
    You should also try to learn the MOA dials on your scope rather than counting clicks.
    If you use one of the "on line calculators" such as JBM to produce a custom drop chart for YOUR rifle it will make life much simpler.

    Dave




    JBM - Calculations
     
  6. Long*range*Lapua

    Long*range*Lapua Member

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    Thanks for the helpful info. Looks like if I go with a 20moa base then I will be at or near the bottom of verticle adjustment....any problem with this optically?
     
  7. RDM416

    RDM416 Well-Known Member

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    Not with a Nightforce.:)