LGU wandering zero

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

  1. Cooper_dan

    Cooper_dan Well-Known 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)
     
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  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.
     
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  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.
     
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  6. pbrown

    pbrown Bunghole

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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 Well-Known 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 Well-Known 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:
     
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  12. springboy

    springboy Member

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    They don’t seem to be well made with all the problems they have. Soft comp tubes,cocking linkages,barrel lead in non existent. Not good for a German gun when compared to HW97. Try getting spares for them as well. I’m on the lookout for a new comp tube after mine failed and left my LGU in an unsafe position. Accurate though lol
     
  13. Adam

    Adam Well-Known Member

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    I disagree, I think they are generally well made. They do suffer from a few design flaws.
    Early comp tubes weren’t hardened around where the cocking shoe fits. It doesn’t need to be hardened anywhere else just there. I haven’t had an issue with it on mine though and they fixed that quite early on.
    I’ve heard of rivets coming loose on cocking lever, fair enough, but again I haven’t had an issue.
    Yes lead in isn’t great on some.

    Breech lockup is fine. Springs are nicely finished, coils flattened and ground flat. Guides are generally a decent fit. I like the way the guide is clamped in the trigger block so it can’t jump off and slam back if there isn’t enough preload. Seals seem good quality but are very tight out of the box.

    People moaned about the cast alloy trigger block but it’s a very precise casting and is a good solution for holding all the sears and pivots in place. It’s a lot less fiddly to reassemble than trying to line everything up inside the Rekord casing too, which is at the end of the day a fairly rough steel stamping.

    The trigger is actually pretty decent too. It takes some fiddling but can get close to a Rekord break just by adjustments.

    I agree about the spares situation. Umarex should insist their distributor handle spares better, though you can (for now) import them from the continent.
     
  14. Nick G

    Nick G Active Member

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    My TX front stock screws , I counter bore and use an insert that takes a countersunk head, and sits flush with the inside of the stock so they can be locked up tight without compressing the wood excessively.
     
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  15. FPoole

    FPoole Active Member

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    I have an old MarkI that has inserts that go through to the bracket. The original screws fit the counter bore perfectly and they seem to lock up nicely without any heavy tightening. I suspect it is something to do with the material. This gun is extra accurate and I wonder if it's a coincidence.
     
  16. Nick G

    Nick G Active Member

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    To my mind its so the screws can be locked up with consistency, I also have a pillar attached to the rear stock fixing that locks up in the same manner and is a snug fit in the stock hole , to prevent any movement fore and aft .
    Having said that this morning I noticed some distortion in the front bracket , so going to make a steel one now . Springers are high maintenance , it never stops :)
     
  17. garym

    garym Active Member

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    I agree, I also think they are generally well made. I love shooting mine, as much as some of my expensive pcp's.
    Trigger is a pig to set up, slowly it is getting there. Great rifle, excellent potential.
    I read somewhere on here about the 'best standard trigger set up', can I hell find it!

    Great rifle, well worth the money and a little bit of tinkering.
     
  18. Adam

    Adam Well-Known Member

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    I think Bri Samson posted something years ago when the LGV came out. I posted a couple of comments about how I tackle mine a few months ago, but it was on someone else’s thread. Been meaning to do a video on it actually. It’s really all about the second screw.
     
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  19. Joha

    Joha New Member

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    I wrote it down

    tighten screw 3 = make trigger heavier unscrew screw 2=no 2nd stage. Tighten screw 1 in small increments until the gun won't cock,
    Unscrew 1 in small increments until it will just cock.
    Screw in screw 2 in small increments until you reach the point where the gun won't cock, then back it off in small increments until it will just cock.

    work how many turns you'd have to give screw 1 and 2 to get a trigger with a short 1st stage and a crisp 2nd stage with no creep... Once you had that, you could unscrew 3 ( trigger weight adjustment could wound out complete), until the 2nd stage weight is how you like it.
     
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  20. Adam

    Adam Well-Known Member

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    OK, I do it completely differently! Are your screws 1 and 2 the little ones in the trigger blad (front and rear respectively)?

    I wind the front screw in until I get the overall length of travel (from rest to break) to where I want it. Usually 3-4 full turns. This will generally lose the 2nd stage. I then wind in the rearmost screw until I get a 2nd stage back , and then in tiny increments wind it out until the break is as crisp as I want. I then tweak the weight. e.g. if the 2nd stage break feels perfect but sometimes snags, (i.e. trigger goes floppy and won't reset if you release pressure rather than firing), I might add a little weight to get it back.

    I sometimes do 90% of the above with the trigger unit outside the gun, settting it with the aid of the long end of a 7mm allen key or similar, but you don't know how it actually feels to shoot, until you shoot it.
     
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