7mm question/problem

Discussion in 'Gunsmithing' started by earl1704, Apr 3, 2017.

  1. earl1704

    earl1704 Active Member

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    New gunsmith built 7mm Remington Mag.
    At first the bolt would not lock on round then would not extract case when it did lock on the round. Gunsmith fixed that problem 'sort of' bullets load but won't extract factory loads half the time but will extract handloads most of the time.

    Bullets hit target sideways....everyone..... point orientation variable. 50 yard target placement.

    Blackhole Weaponry barrel 1:10
    Polygonal rifling
    700 action
    Bell & Carlson stock.
    Trigger is a rebuilt (unknown origin)

    Shot in rifle;

    Factory bullet, Winchester 175 gr.

    Handloads
    Nosler brass
    WLRM primer
    Berger Bullet Hunter Classic 168 gr.
    H4831 SC 62 gr

    Has muzzle break installed.

    The rifle is beautifully built but bullets hitting 16 X16 target at 50 yds, right, left bottom no pattern at all, but all hit sideways. At 100 yds could not hit paper at all.

    Barrell problem?

    I have taken the rifle back to the gunsmith to fix the other problems (kind of) but what would cause bullets to always strike sideways? Could the extraction problem also be part of an overall barrel problem?
    Any thought or help would be appreciated.
    Earl L.
     
  2. Barrelnut

    Barrelnut Well-Known Member

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    That's pretty bad. I have a couple old guns that are shot to heaven and they still do better than that.

    Maybe a 7mm chamber was cut on a 30 cal barrel by mistake? A 10 twist on a 7mm is very slow. Should be 9.25 minimum, IMO. 10 twist is usually for 30 cal.
     
  3. shortgrass

    shortgrass Well-Known Member

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    The rifling is not stabilizing the bullets, hence, they hit the paper every way but nose first. The 1-10 twist is not correct for the bullets you have chosen. Try a lighter weight bullet and see what happens. Did you choose the Blackhole weaponry barrel ? If, so why?
     
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  4. earl1704

    earl1704 Active Member

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    The gunsmith choose the barrell I trusted his expertise, the 1:10 twist is supposed to be OK for a berger 168 gr bullet but the Winchester 175 gr did not have a twist rate on the box. I did tell the gunsmith I wanted to shoot long range 1000 yds or less mostly at metal gongs. I do hunt however and would have liked to shoot heavier bullets 200 or 220 gr.
    The twist not stabilizing the bullets seems to be correct but again I ask why? Berger says on the box 1:10 would be ok for a 168 gr classic hunter VLD but no heavier of a bullet, my handloads are well within specs. I have loaded for many years and load to very tight tolerances.
    I would have liked a 1:9 or faster twist but that's a discussion I will have (very loudly) with the gunsmith.
    Is the barrel just bad and it there a way to tell?
    Earl
     
  5. Dosh

    Dosh Well-Known Member

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    1704, perhaps dropping a loose 7mm bullet in the muzzle would check the .30 cal theory. Otherwise check barrel threads tightness or muzzle brake loose. Bullets tumbling @ 50yds screams wrong caliber barrel. If so, easy fix would be to rechamber to a .30 cal magnum. Hope you find a reasonable cure.
     
  6. calhunter805

    calhunter805 Well-Known Member

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    Nobody makes a 200 or 220gr 7mm bullet other than the old wildcat and Alco bullets. Also I would measure the bore of the barrel it almost sounds like its 30cal. It should at least be close enough with a 1-10" twist to not tumble the bullet but maybe not group anything, your on the ragged edge of stabilization in my opinion with a 168gr and 1-10".

    Any gunsmith that tells you a 1-10" twist 7mm is ok for shooting heavy bullets is not a good smith to use. Also why did he choose a blackhole barrel? that would have been my first RED FLAG to not use him.
     
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  7. shortgrass

    shortgrass Well-Known Member

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    Could be that polygonal rifling. I see NO reason to venture away from 5R or conventional rifling. 7mm deserves a 1-8.5 or 1-9 twist. What it says on a box of bullets, concerning twist, isn't 'set in stone',,, it's a 'suggestion' or guidance.
     
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  8. shortgrass

    shortgrass Well-Known Member

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    Could be that polygonal rifling. I see NO reason to venture away from 5R or conventional rifling. 7mm deserves a 1-8.5 or 1-9 twist. What it says on a box of bullets, concerning twist, isn't 'set in stone',,, it's a 'suggestion' or guidance. The combination of 1-10 twist and poly rifling could be what's giving you 'fits'. I don't know how a 'gunsmith' uses the wrong caliber barrel, but anything is possible these days.
     
  9. Kmccord

    Kmccord Well-Known Member

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    Is the barrel stamped with a caliber? It definitely sounds like the barrel is a .30 caliber, no other reason for bullets to tumble, unless you have no rifling at all. I would do as other suggested and see if a loose 7mm bullet will slide through the barrel or take some calipers and measure the inside diameter.
     
  10. Dosh

    Dosh Well-Known Member

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    1704, have you tried this ^ test?
     
  11. Cuz

    Cuz Well-Known Member

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    If you have a muzzle brake, make sure the bullets are not hitting it. Could be the problem.
     
  12. Barrelnut

    Barrelnut Well-Known Member

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    lightbulblightbulblightbulblightbulblightbulb
     
  13. Dosh

    Dosh Well-Known Member

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    1704, have you discovered the problem??
     
  14. earl1704

    earl1704 Active Member

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    Tried all the suggestions, the 7mm bullet will not go into the barrel other than the tip, cant see any wear or impact marks on the muzzle break. No stamp on the barrel to indicate caliber.
    I called the barrel marker and asked what was ordered and the gunsmith ordered a 1:10 so that's on him. According to the barrel maker polygonal rifling is the latest and greatest thing but the etching inside the barrel is barely seeable but they said it supposed to be that way. Ran a dry patch down the barrel to see what the twist would/should be the patch would not turn even a little.
    On a later call to the barrel maker I told them what was happening instead of the usual 'the stars are not I correct alignment' or it 'must be the ammo' or some other excuse they said to return the barrel and they would replace it. Did not need to coerce them or argue...........just "we will replace it". Some how or someway something is wrong with the barrel they just don't want to say what. In this life as they say s*%# happens so if they are willing to stand behind their product I ok with it. The gunsmith that's another story...................Thanks for you help and input...........Earl