LGU wandering zero

Discussion in 'Piston & Spring' started by Cooper_dan, Mar 1, 2019.

  1. Cooper_dan

    Cooper_dan Active Member

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    A short story, just in case anyone else finds themselves with the following issue, this is a relatively easy thing to check!

    Had my first extended play with the new to me LGU today and had the dreaded wandering zero!
    Was shooting at an 8mm bell target at about 20 yards. Got it zero'd and was hitting the bell happily enough, then it started only ringing every other shot, then it stopped ringing at all. Went to have a look and the pellets had been walking up and out of the target. Zero was now about 10mm higher than it had been.

    Re-zero'd and started again. After about 20 shots the same thing happened again. Zero moved out the top of the target.

    Put 40 shots over the chrono and it was very consistent between 752 and 764. No problems there. So I started to strip it down to see if I could find anything inside. Luckily I used my torque screwdriver and noticed that one of the screws had relaxed (from my normal 1.5 Nm to 0.8Nm).

    Instead of stripping it down, I nipped up the screw and started shooting again. The zero was now below the target (i.e where it had started). After about 30 shots it had come up and started ringing the bell again. Checked with the torque screwdriver and the same screw had loosened to 0.9Nm.

    This time I torqued all 3 stock screws up to 2Nm. About 50 shots later they appear to have stayed put. All are still at 2Nm. The value of 1.5Nm that I always use is for my TX200 that's in a beech stock. This LGU is in laminate so maybe that's the difference? Having thought about it, I will probably up it to 2.5Nm for the weekend just to be safe.

    (Before anyone suggests it, I don't like using loctite on stock screws. I shoot in the rain a lot so have to strip the rifle down a lot. CBA with cleaning loctite out of the threads every time)
     
    garym, Adam, pbrown and 1 other person like this.
  2. RobF

    RobF Administrator Staff Member

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    My hw and tx only run one bolt under the action in the custom stocks. The hw is pillar bedded and the tx might be as well (can’t remember). It solves the issues with the wood changing and pulling the muzzle around or just wearing with the recoil. Standard beech or walnut seems to be less problematic but the fit for target work isn’t as optimal.
     
  3. Adam

    Adam Well-Known Member

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    Would like to see some photos of the pillar bedding if poss. It will wait til after Sunday though :D
     
  4. tillygti6

    tillygti6 Tilly's gun stocks

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    Dan ,I posted on here a good year ago about the front fixing screws having to be evenly torqued up.

    Chances are, the one that works loose isn't counter bored square to the actual bolts head ?

    The bolts on all the walthers(mainly lgv tbh) I've seen arnt angled the same on both sides.
     
    Cooper_dan likes this.
  5. RobF

    RobF Administrator Staff Member

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    I'll see if i can get into the gun cupboard tomorrow and hook the 97 out.
     
    Adam likes this.
  6. pbrown

    pbrown :)

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    I had an LGU in a standard beech stock and during a weekly check always had one screw that needed nipping up, IIRC the one underneath by the trigger.
     
  7. Cooper_dan

    Cooper_dan Active Member

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    You could be right. The inletting on the whole is pretty shoddy. Looks like the cutter used has taken chunks out of the wood instead of cutting clean.

    Going up to 2Nm seems to have sorted it
     
  8. Adam

    Adam Well-Known Member

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    Never had the stock bolt zero shift on the LGU Warren stock, since he started having the Murph do the inletting.
     
  9. Nomads HFT

    Nomads HFT Well-Known Member

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    Here's the thing; regardless of whether the stock bolt screw holes are in the right place, or at the right angle, or not, stock screws don't unscrew themselves - something has to happen to unscrew them, which has to be vibration during the shot cycle.

    Is it a question of the magnitude of the vibration, or the frequency, or a combination?
     
  10. blacklab

    blacklab Active Member

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    These springers are a headache up down in out all over the place:D
     
  11. Cooper_dan

    Cooper_dan Active Member

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    Nope its fine now :D
    This one is new to me and it just needed a different setting than I'm used to.
    Once they are set up the only headache is people messing with them :rolleyes:
     
    pelletcaster likes this.

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