Hot barrel stringing shots

Discussion in 'Gunsmithing' started by rharfo, Jun 20, 2015.

  1. rharfo

    rharfo Well-Known Member

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    Got a old Browning A bolt in 308 with a factory pencil thin 22 inch barrel. When the barrel heats up it strings shots high. Will bedding the barrel/action help stop or slow this down? Other then shooting slow will anything help? If I start slinging lead in the warm months at a ground hog or coyote I would like it to not be shooting 2-3+ inches high.
    Thoughts?
    Thanks
     
  2. Barrelnut

    Barrelnut Well-Known Member

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    I have an old Browning A bolt in 7mag that behaves the same. I believe it is because the barrels are hammer forged and it is impossible to completely stress relieve a hammer forged barrel. Though maybe they are better at it these days. But I don't think there is a cure other than keeping the barrel cool.
     
  3. J E Custom

    J E Custom Well-Known Member

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    As the weather warms up so does the ammo. This may be your problem.

    As you shoot keep the ammo in a cooler (The freezer packs work well wrapped in a towel and placed in the bottom with the ammo on top.

    The other thing is when you are shooting, don't let the ammo "Cook" in the chamber. get your position, chamber the round and shoot as soon as possible. If you feel the round has been in the chamber to long, eject it and chamber another round.

    Higher powder temperatures will increase pressure causing a change in POI.

    If this doesn't help, then a good bedding and barrel float may be in order.

    J E CUSTOM
     
  4. rharfo

    rharfo Well-Known Member

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    Thanks guys
     
  5. jfseaman

    jfseaman Well-Known Member

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    All the things JE said.

    and

    Wait a long time between shots. 2 minutes or more.

    For "real" testing prior to hunting I wait as long as 20 minutes+. My range has a target break every 20 minutes. I take multiple rifles including a 22 to shoot while I wait.
     
  6. Barrelnut

    Barrelnut Well-Known Member

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    The original A-bolt only has "one" bottom screw that torques the action to the stock. and it is glass bedded at the factory to insure the recoil lug is flat against the stock lug stop. The rear action screw actually screws into the trigger mechanism and if you put much torque on it the trigger will start locking up. So bedding will not help.

    The barrel is also free floated from the factory with ample room to spare. Always good to verify though. If you are having general accuracy issues from a cool bore, one thing that can help an A-bolt is to actually but something between the barrel and stock forearm that takes to free float away. This just seems to help on pencil barrels sometimes. Problem with this though is that the stringing will get worse as the barrel gets hot.

    Long thin Browning barrels are known to "walk" as they heat up. They are not made for high volume shooting. They are made for general carry hunting. I think it would be fine for some wood chucks or coyote hunting as the barrel could probably cool between shots, but prairie dogs, probably not.

    The biggest pain can be getting them sighted in with a cold bore. Cause if not careful, ,during a sight in session, you may get it zeroed with a fairly warm bore and the POI will change significantly when the time comes for a cold bore hunting shot.

    Are you reloading or using factory ammo?
     
  7. rharfo

    rharfo Well-Known Member

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    Factory as I had a bunch of federal 150 nbt given to me
     
  8. Barrelnut

    Barrelnut Well-Known Member

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    Nosler bullets usually shoot very well. I shoot 160 Accubonds in my A-Bolt in 7RM.

    An A-Bolt in 308 with a 22in barrel would be a quick and handy rifle. If the barrel walking gets to be a big issue. Maybe the best thing to do would be talking to a smith about a new barrel. A button rifled 24in barrel in maybe a light varmint profile would probably cure the walking issue and allow higher volume shooting for range practice and wood chucks and such.
     
  9. rharfo

    rharfo Well-Known Member

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    anybody know what the best torque on the stock bolts should be??? I don't recall is shooting this bad years ago... i just put in back in the stock after having a new pad installed...
    wood stock that is
     
  10. Barrelnut

    Barrelnut Well-Known Member

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    With wood, I would go no more than 35-40 on the front one. Might want to torque the back one to 25 and then start tightening it up a bit as you shoot to see if there is a sweet spot for it. I don't think Browning publishes and specific numbers for torque.
     
  11. rharfo

    rharfo Well-Known Member

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    Thanks I'll give it a try