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Thread: Case head seperation, .22 semi-auto

  1. #1
    Member ROKTOY's Avatar
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    Case head seperation, .22 semi-auto

    Sportco Model 73A .22 semi auto.
    The rifle suffers from case head separation.
    Inherited it from a family member 10 plus years ago with part of a casing stuck in the chamber, the head of the case had been pulled off by the extractor. I had the remaining section of casing removed by a gunsmith and it functioned ok for a bit.
    It has now been in the safe for a while as it has suffered case head separation again and has another partial case stuck in the chamber. I have probably only put 30-40 rounds through it. (homekill muttons)
    So it seems to me the chamber is too tight and needs to be opened up a bit. But it requires the stuck case extracted first.
    Rifle is in reasonable used order for a 30 plus year old.22, a bit of light pitting on the outside of the barrel, timber has a few marks and scratches but no major damage.
    Pinned barrel,
    threaded for suppressor
    10 round mag
    Do I persevere with it or not?

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  2. #2
    Member Marty Henry's Avatar
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    Any photos of extracted and separated cases? Apart from that I guess you are using supersonic ammo, have you tried subsonic will it cycle with it and does the same thing happen.
    It could be that the recoil spring is weak this could happen if it was stored with the bolt locked open.

  3. #3
    Large Member mimms's Avatar
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    I assume you've tried cleaning the bejesus out of the chamber?
    I doubt it's a tight chamber. Do unfired rounds extract easily?

    I would have the chamber re-cut, either way, and headspace the bolt and it'll go for another 30+ years.

  4. #4
    Member Tussock's Avatar
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    Been dry fired and burred the chamber below the firing pin?
    “Practical men, who believe themselves to be quite exempt from any intellectual influence, are usually the slaves of some defunct economist. Madmen in authority, who hear voices in the air, are distilling their frenzy from some academic scribbler of a few years back.” John Maynard Keynes

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    Just a tip, If we need to remove brass or bronze bushes from machines at work we just heat the bush and let it cool down. Brass and bronze will cool to a smaller size and usually just fall out. Wouldn't take much heat on a case to heat the thin wall of it. May be an option if you want to try removing it yourself.
    ROKTOY likes this.

  6. #6
    Member ROKTOY's Avatar
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    Quote Originally Posted by Marty Henry View Post
    Any photos of extracted and separated cases? Apart from that I guess you are using supersonic ammo, have you tried subsonic will it cycle with it and does the same thing happen.
    It could be that the recoil spring is weak this could happen if it was stored with the bolt locked open.
    Subsonics only.
    No cases to photograph, damaged one still in chamber. snapped off level with rear of chamber.
    Stored with bolt closed, Previous owners may have stored differently.

  7. #7
    Member ROKTOY's Avatar
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    Quote Originally Posted by Tussock View Post
    Been dry fired and burred the chamber below the firing pin?
    worth checking, thanks

  8. #8
    Member ROKTOY's Avatar
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    Quote Originally Posted by mimms View Post
    I assume you've tried cleaning the bejesus out of the chamber?
    I doubt it's a tight chamber. Do unfired rounds extract easily?

    I would have the chamber re-cut, either way, and headspace the bolt and it'll go for another 30+ years.
    Yes has had good cleans. most rounds extract fine, fired and unfired, until one doesn't and this happens

  9. #9
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    How old is the ammo? There have been various batches in the last 10 years that gave consistent rupturing problems due to improper case annealing during manufacture. A bronze brush from the muzzle will usually push ruptured .22 cases out. Try some fresh ammo before anything else. I doubt that it is a chamber problem.

  10. #10
    Member Cordite's Avatar
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    Has it been used for .22 Shorts? They can pit the front of the chamber and cause .22LR to stick.

    Alternatively, see if you can at all doctor the mag to take 10+ and bring it to the buyback: thin replacement coke can concave aluminium follower, light gauge homemade spring with fewer windings.

  11. #11
    Large Member mimms's Avatar
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    Quote Originally Posted by ROKTOY View Post
    Yes has had good cleans. most rounds extract fine, fired and unfired, until one doesn't and this happens
    Wild Ass Guess is loose or too-smooth (or off-axis) chamber coupled with slack headspace. Brass expands and sticks at the front of the chamber while the rest of the pressure takes the rim/ head backwards. By that time the bullet's out the barrel and pressure has dropped but the ring has undergone plastic deformation/elongation, so it stays there.

    That's my theory, anyway.

    Any powder/carbon (blow by) on the outside of fired rounds?

  12. #12
    Member ROKTOY's Avatar
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    Quote Originally Posted by mimms View Post
    Wild Ass Guess is loose or too-smooth (or off-axis) chamber coupled with slack headspace. Brass expands and sticks at the front of the chamber while the rest of the pressure takes the rim/ head backwards. By that time the bullet's out the barrel and pressure has dropped but the ring has undergone plastic deformation/elongation, so it stays there.

    That's my theory, anyway.

    Any powder/carbon (blow by) on the outside of fired rounds?
    spent casings are clean, well those that I have managed to locate after firing.

  13. #13
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    I wonder if this has been a long-term problem , and repeated abrasive cleaning of the chamber has created excessive chamber space , coupled with sloppy headspace.

    Sportco rifle have a pretty good reputation usually so there has to be some out of the ordinary issue going on here.
    Cats have nine lives-which makes them ideal for experimentation...

  14. #14
    Member ROKTOY's Avatar
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    @muzza, I have only heard good things about Sportco rifles too. This one doesn't appear to have too much use. I don't use abrasives as it only fires limited rounds on the farm knocking over home kill muttons. Well it used to. replaced it now.
    I think this one can go

 

 

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