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Thread: Help! 308 will not zero with mod.

  1. #1

    Help! 308 will not zero with mod.

    I have a Blaser r93 with .243 and .308 barrels, I have one jet-z mod in 30cal that is proofed for both barrels, it is shooting very well with the .243, but am unable to adjust my cross hairs enough to get a zero with the 308, with out the mod the 308 shoots fine and I can easily get a zero. The bullets are 150g SP, when I scale down to 120g BT I have just enough movement on the cross hairs to get a zero. Would welcome any advise as I want to shoot bullets at around the 150g, and I do not want to buy another scope and mounts due to cost, currently have a Swazoski 8x56. Hope some one can help.

  2. #2
    Are you sure the barrel has been threaded correctly?

    if its even slightly off it can make a huge difference.

  3. #3
    Fire a group without the mod on, then fire a group with the mod on. How far does the group move? Does it still group?

    How near are you to the scope's maximum adjustment without the mod on? And is it windage or elevation that you have run out of adjustment for (or both)?


  4. #4
    Alex, With the mod on the the group moves about 24" to the bottom right, so run out of both adjustments, rifle still groups all be it not as well.
    Thanks Jon

  5. #5
    24", that does seem a lot.

    To put it into perspective, my .30-06 moves about two inches right, two inches up.

    Presumably you don't get the same shift with the .243 barrel?

    If it was the mod interfering with the bullet then it wouldn't group at all, so whatever is happening is happening semi-consistently and only with one barrel

    Could it be the weight of the mod is causing contact between the .308 barrel and the stock? Is the outer barrel profile different between the two barrels? Either that, or the threading/moderator to barrel interface like Bobt says?

    Not really my area of expertise to be honest!


  6. #6
    2 ft at hundred yards! wow. I would say, do not fire another shot with the mod on your 308 barrel.
    Get it checked out that there is no mechanical fault.
    2ft is more than a stock touching and more than a mod should or possibly can do because of its weight.
    Sounds more like a crooked mounted mod or a loose barrel. If it is not scope mount related.


  7. #7
    Its either an issue with the mount to that specific barrel or the screwcut, the mounts have 12MOA elevation as standard (a litttle known fact) but that still doesnt equal your drop and it would be high instead of low!!!!!

    I would say there is clipping due to the screwcut being not alligned or poor machining of the mount recesses.

    Two questions: is the .308 barrel factory threaded & you say 120gn BT, im unaware of anybody that makes a 120gn BT in 30Cal?

    Either way do not use it any more untill investigated by a riflesmith.

  8. #8
    I'd get it looked at too - but check scope mounts etc first, 24" at 100 yds is a lot of clicks! You could try shimming the scope, but that's far from ideal.

  9. #9
    Swarovski had a problem with some reticals on moderated rifles due to the different recoil harmonics and they changed the glass retical to a different material but I doubt that you would maintain a group and don't know which scopes were affected.

    Check action screws.

    How tight are you fitting the moderator but 24in is serious cause for concern.


  10. #10
    i think more than 4" impact change is highly irregular and totally unacceptable, jackson rifles may be able to advise what is acceptable/normal. cant offer any more than that, but a good riflesmith may!

    i run 2 fully assembled blasers and i have another barrell, scope, mount and mod awaiting collection, i would definately advise another scope and mounts for your 2 calibres(its ok to share mod if its working ok), you have one of the most accurate and consistent hunting rifles available - why frustrate yourself by pissing around changing the scope between barrells and re-zeroing every time. the blaser saddle mount will go off and on its zeroed barrell without loosing zero, but i'm sure they never intended people to swap scopes between calibres - its just a ballache that you dont need - and even high end scopes cannot be trusted not to miss a click. a friend has 3 barrells and 2 scopes/mounts and his intention was to keep 1 setup and swap the other scope between 2 calibres - there are 50 clicks difference between the two, its just too much of a difference.

    in my humble opinion of course!

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