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Thread: moderator effect on grouping?

  1. #1

    moderator effect on grouping?

    Would people expect a moderator to have any effect on grouping?

    I have a recently aquired Tikka in .222, with an Ase Utra mod, and the grouping appears to go from around 0.75 inches at 100m to around 2 inches when I put the mod on.

    Any ideas as to why this is?

  2. #2
    could be the mod took off enough velocity to affect grouping, you might try (assuming safe and no pressure signs), bumping up the powder to offset the effect of the mod.

  3. #3
    Don't sound right to me, in some cases the zero may well drift off but the groups do not usually differ by that much. I have been very lucky and have never had any variation to my zero/groups with the mod either on or off. Did you get the thread cut or was it already done.

    PKL why would the mod reduce reduce velocity, I don't understand.

    A clever man knows his strengths, a wise man knows his weaknesses

  4. #4
    sounds like the weight of the mod is making the barrel contact the stock causing bigger groups ,just my thaughts on it, atb wayne

    did you have the threading done or was it already done when you got the rifle ,can you see any telltale signs of the bullet clipping the mod as that also will effect it if the screwcutting hasnt been done true
    Last edited by mereside; 24-09-2012 at 12:38.
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  5. #5
    Only takes your threading to be slightly off to put more pressure on one side of the bullet than the other - even if there's no sign of it clipping on exiting the mod.

    The threading could also be misalligned within the actual moderator on certain models.

    Try a different moderator - if you get the same problem then re-thread and re-crown from Mr Norris I reckon... if changing the mod fixes the problem then send your mod back to the supplier and ask for a replacement.

  6. #6
    Hi John,
    What make mod are you using? I use s T8 and groups alter if i take the mod off/on.

  7. #7
    To add to the symptoms which may help diagnosis: there is a consistent pattern to the shots. First shot goes an inch high and a touch right. Second shot bang on, third shot half an inch low.

    Rifle was factory threaded and was 'nearly new' when bought (probably less than 100 rounds through it).

  8. #8
    I need to agree with JAYB on this. While not very well versed in moderators, I can't see a substantial (if any) reduction in velocity by adding one. Adding powder to compensate could be dangerous. Chamber pressure is independent of end velocity when it's mechanically reduced. (ie: A short barrel will reduce velocity but the pressures will be the same) I vote for a bedding issue.~Muir

  9. #9

    It sounds a bit odd, I would expect the group to be smaller and at a different POI with the mod on. I would recommend taking a run through to Alex Dalgleish in Eaglesham and ask him to sort it out. Secondly, once you've got it working, I would recommend using the moderator all the time. The only time my rifles get fired without the moderator on, is when they go to proof.

    Regards JCS

  10. #10
    No velocity reduction with a moderator, recoil reduction yes but that has nothing to do with bullet velocity.
    Worth checking how the rifle performs with and without the mod as the mod will affect the 'barrel time' and maybe move or spread your group out.

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