Cold Bore Improvment

Discussion in 'Long Range Hunting & Shooting' started by Clayne B, Jul 24, 2012.

  1. Clayne B

    Clayne B Well-Known Member

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    Im sure this has beaten to death already... But I have done about everything i can think of about my cold bore shot. many changes have been made to my gun with not much change... (CZ 452 Scout, .22lr) My cold bore shot used to be all over the place. Now after all the things i have done to my rifle over the last six months... stock, trigger kit, bedded action. tried different cleaning techniques. I am now down to this... My cold bore is half a mil high at 25 yards. If I let the gun sit for just a few min the first shot is half a mil high.... and the rest of the shots are spot on! WTF! any input would be appreciated.
     
  2. Bullet bumper

    Bullet bumper Well-Known Member

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    That is a hard one to work out.
    Try the gun with a normal magazine and not the single shot adapter.
    Try different brands of ammo .
    Try not cleaning as much as rimfires don't need to be cleaned very often like centerfires do.
    It is strange that letting the gun sit a while causes a high shot . That would indicate heat is an issue but rimfires don't get that hot anyway and one would think the zero would go up with sucessive shots if heat was an issue.
    Does your CZ have a screw under the forend infront of the reciever ring ?
    If it does then maybe you should try altering the tension on that front screw to see if anything gets better or worse.
    Also some CZ's have no support between the stock and the action under the middle screw and if this screw is too tight it bows the action and stock .
    I am guessing here because I am not familiar with that specific American scout model . It may be different to my Brno Cz's over here .
    .5 Mil at 25 yards is only about .45 inch . Are you sure you are shooting well enough to see that .45 inch difference all the time.
    Don't ignore the scope either they do some crazy things.
     

  3. Clayne B

    Clayne B Well-Known Member

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    I am using a 10 round mag,
    No barrel tension srew. it is free floated.
    I have shot it clean cold bore, and not cleaned in 1000 rounds, and it is the same
    I am shooting CCI SV, it has proven to be very accurate ammo in this rifle
     
  4. Bullet bumper

    Bullet bumper Well-Known Member

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    It can't hurt to try some other ammo .
    If the ammo and the scope are ok then it has to be either a bedding issue or something strange about the way the bullet chambers when the gun is cold or weird barrel vibrations when the barrel is cold .
    It may be one of those weird issues that can't be easily identified.
    If all else fails and you have done lots to fix the problem then maybe you should think about selling the gun or if you still want to keep it get an inch cut off the barrel tos ee if it changes the harmonics . Rimfires don't usually have much barrel harmonics due to the low pressure round but who knows what this gun is doing.
    CZ's sometimse have very tightly fitted barrels . They put them in at the factory with a machine that locks them up very tight . Well mine are that way. I removed the barrel from one of my Brno Cz's and it was as tight as hell. In the end I reckoned it was so tight it was distorting the action . So I lapped the barrel threads to a nice even and better fit and accuracy did improve some what . It was quite accurate before but it got better after releasing that tight barrel stress on the action ring.
     
  5. WildRose

    WildRose Well-Known Member

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    Simple, always fire at least 2-3 fouling shots after a good cleaning before you go back to shooting for accuracy. If anything that's what the CCI SV's are good for.

    If you do a little reading you'll find it's some of the worst .22lr ammo on the market for consistent velocities.
     
  6. WildRose

    WildRose Well-Known Member

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    Have you bedded the action?
     
  7. Bullet bumper

    Bullet bumper Well-Known Member

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    In the initial post he says it shoots high after being left unused for a short time even after firing many shots ? So after it cools down the first shot is high each time . A fouling shot will not fix that scenario because many shots have been fired.
    I am also thinking that any ammo change might be worth a try .
     
  8. WildRose

    WildRose Well-Known Member

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    The CCI SV's are so inconsistent I wouldn't put much stock in any results achieved with them which is why I suggest the ammo change.

    I've shot many, many different rifles over the years from pawn shop rack guns to the very finest weapons our military could produce.

    I always found the same recipie works best for all which is to never shoot for accuracy and consistency without a few fouling shots unless you are one of those guys who plans to clean between each shot.

    Even .22lr Match Ammo is designed for 100yds or less here and most .22lr matches are shot at less than 50yds.
     
  9. Clayne B

    Clayne B Well-Known Member

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    I did some cleaning on the gun to night, I mopped it with hoppe's 9 and brushed the phuck out of it with a nylon brush. and did a 2 passes with the bronze brush. then ran some easly fitting patches followed by some tight fitting. i was getting lead slivers and little chunks of black stuff out. I repeated this process a few times. I should get a chance to go shoot it tomorrow. I think this is the cleanest this rifle bore has ever been in its life.
     
  10. RMulhern

    RMulhern Well-Known Member

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    Once 'pon a time I knew a fellow, a smallbore outdoor champion that won more 1600 aggregate championships than the law oughta allow. When asked one day how often he cleaned his .22 match rifle....he replied..."I don't!" At that time he stated he had over 80,000 rounds fired through it!!

    FWIW!!lightbulb
     
  11. WildRose

    WildRose Well-Known Member

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    Damn he's worse than me. I at least clean my 10/22 when it starts being contrary about cycling! gun)
     
  12. Clayne B

    Clayne B Well-Known Member

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    I went out and shot.
    93 degrees
    Durring wait time the rifle and ammo were in the shade. and i was working on my tan.
    Shot prone with bipod and rear bag.

    [​IMG]

    [​IMG]
     
  13. WildRose

    WildRose Well-Known Member

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    What range were you shooting at?
     
  14. Clayne B

    Clayne B Well-Known Member

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    25 yards