New crown affect on loads

Discussion in 'Reloading' started by Preda8or, Jun 15, 2006.

  1. Preda8or

    Preda8or Well-Known Member

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    If I had a 11 degree crown cut will it affect what loads my gun likes?
     
  2. gonehuntingagain

    gonehuntingagain Well-Known Member

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    If the barrel was cut back some, it might change the harmonics enough that you will need to re-tune your loads slightly.
     

  3. larrywillis

    larrywillis Well-Known Member

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    There's no magic with an 11 degree crown. The exit at the muzzle needs to be crisp and clean. The most important thing is that it needs to be cut so that it's concentric at the muzzle. An 11 degree crown looks very good, but unlike a squared off muzzle it's a bit more difficult to do.

    An 11 degree crown can only be cut by using a steady-rest attachment on a lathe. That's the only way to get it concentric.

    - Innovative
     
  4. Bart B

    Bart B Well-Known Member

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    It probably won't effect to any noticable degree what load your rifle likes. Years ago a few folks tested the same rifle/ammo with crown (actually muzzle face) angles from 0 to 15 degrees in 1 degree increments. After each angle was cut, the rifling was lapped smooth with a grit coated ball to smooth up the edge of the lands. Tests were made with 20-shot groups. As the angle was increased to the maximum, barrel length didn't change more than about 1/10th of an inch. The medium weight 26-inch barrel used didn't change its resonant frequency more than about 8/10ths of one percent. All the test groups were under 4 inches at 600 yards but the smallest happened at 10, 11 and 12 degrees; so 11 degrees seems about perfect.

    Proper muzzle crown/face jobs require a centering pilot of exact bore diameter be put in the muzzle then held by the tail stock of the lathe. This lets the muzzle outside diameter be turned parallel to the bore so it can be held in a steady rest. Bore/groove surfaces turn in a perfect circle when held in the steady rest so the cutting tool perfectly centers the crown. And always cut from the bore outward. If you don't turn the muzzle on bore center, a flat (0 degree, at right angles to the bore) crown is probably best.
     
  5. EddieHarren

    EddieHarren Well-Known Member

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    Innovative, I've been cutting crowns on barrels for years and not on steady rests. If you hold the barrel in a 4 jaw chuck and hold the other end in a "spider", both ends of the bore can be indicated for zero runout. The only time I resort to the steady rest is when the barrel diameter is to large to fit through my headstock.
     
  6. strictlyRUM

    strictlyRUM Well-Known Member

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    Ya me too..... After reading that I thaught I must just be lucky? Huh?

    strictlyRUM /ubbthreads/images/graemlins/confused.gif
     
  7. 257speed

    257speed Well-Known Member

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    Doc Ed and Strictly RUM, thanks for throwing that in, I thought I was the only one scratching my head. /ubbthreads/images/graemlins/confused.gif
     
  8. James Jones

    James Jones Well-Known Member

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    I have actualy recut the crowns on several barrel using the jig I built for blue printing actions. Its basicaly the same thing as the Gre-Tan jig just bigger 6" 416 SS bar stock 12" long with a 2" bore. I set the barrel indexed off the bore.
    The hand turned cutters from Brownells are said to be realy good also. Ay of you guys ever try one