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Better Ignition on CZ 455

Discussion in 'Rifle Country' started by Picher, Sep 22, 2019.

  1. Picher

    Picher Member

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    I've been getting some low shots in groups fired from my CZ 455, with .17 HMR, so decided that it was because the firing pin was hitting high on the rim fold, so I ground the top of the pin to eliminate the poorer ignition and, after trying several groups, found that the low shots have been eliminated.

    It's a cure that we've used to eliminate the problem on .22LRs and I was getting them on the .17 and .22 WMR. The groups are now much rounder!

    JP
     
  2. d2wing

    d2wing Member

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    Good to know. Both my CZ's have ruined groups by some shots low. I will have to try this.
     
  3. 351 WINCHESTER

    351 WINCHESTER Member

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    I'll have to keep that in mind.
     
  4. BigBore44

    BigBore44 Member

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    Appreciate the heads up. I just bought a CZ 455. I haven’t gotten to take it out yet. But it’s good info!
     
  5. Picher

    Picher Member

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    I think that some of the low shots may have been caused by the ammo, but not on every group. I'm very pleased with the improvement! All but one 100 yard group was rounder and 1 MOA or less, despite shooting off my portable benchrest on top of a Black and Decker "Workmate". I decided to shoot on the woods road, due to the wind velocity/direction that day.
     
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  6. StrawHat

    StrawHat Member

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    Having trouble picturing what you did. Any chance of a diagram for us unimaginative types?

    Kevin
     
  7. sparkyv

    sparkyv Member

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    Wow! Never heard of such a thing. Learn something new every day.
     
  8. Picher

    Picher Member

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    IMG_4017.JPG

    The firing pin top edge needs to be ground to hit just below the rim fold, which is stronger than just below it. The strike then gives greater force to the area that the back of the case pinches the priming compound against the straight part of the case, making better ignition and flame spread. Hope this helped, even if it's out of scale. Take it easy with the grinding and check it before taking too much off (by using a fired case).
     
  9. StrawHat

    StrawHat Member

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    Got it! Thank you.

    Kevin
     
  10. Kookla

    Kookla Member

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    @Picher This is cool stuff, thank you for posting this. Do you know if the shape of the firing pin matters? I've seen some firing pin indents on rimfires' that were rectangular and some that are circular.
     
  11. Picher

    Picher Member

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    Firing pin noses shouldn't have sharp corners that could pierce a case. Rounded edges seem to work well because they spread the primer flame evenly to make the powder burn more consistently.
     
  12. 22250Rem

    22250Rem Member

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    Very interesting and informative. None of my rimfires currently need any fixing but if I ever come across that condition I'll have to remember that. Especially my CZ-455...... Thanks for posting.
     
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  13. redneck2

    redneck2 Member

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    How complicated is it to did assemble the bolt to remove the firing pin?
     
  14. Reloadron
    • Contributing Member

    Reloadron Contributing Member

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    Thanks for sharing that. Just something I never placed much thought into so again thank you.

    Ron
     
  15. d2wing

    d2wing Member

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    Thanks. one of the most useful posts on here.
     
  16. I6turbo

    I6turbo Member

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    Good info, Picher.

    For others asking, here's about how you want the firing pin strike on the cases to look.

    vju1nyn.jpg

    Here's another shot of a different shape firing pin. You want it like the strike on the right, not the one on the left.
    Ds6hrzw.jpg
     
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  17. Picher

    Picher Member

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    IMG_4019.JPG
    Actually, I didn't remove the pin, but had a very small Moto-Tool bit that did the job well, working very carefully. Took all of 5 minutes, after clamping the bolt in a padded vise.

    The "Before" is on the left and "After" is on the right. (The other pictures recently submitted by 16Turbo show the change better than mine, but I didn't know about it before this.)
     
    Last edited: Sep 25, 2019
  18. redneck2

    redneck2 Member

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  19. WelshShooter

    WelshShooter Member

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    Excellent tip, Picher! I have a CZ 452 which is a great rifle but I never paid attention to my fired cases before. I'll keep my eye on them and see if my firing pin needs fettling.
     
  20. bamajoey

    bamajoey Member

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    It probably won’t need it on the 452. The 455 has a different tip on the firing pin because of using the same firing pin on three different calibers, 22, 22 mag and .17. If anyone needs more info on grinding the tip, Rimfire Central has plenty on the CZ/Brno section.
     
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