Crowning of the barrel muzzle
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Thread: Crowning of the barrel muzzle

  1. #1
    Join Date
    Sep 2018
    Posts
    287

    Default Crowning of the barrel muzzle

    Hi all,
    Does anyone know the science involved around the crown on the muzzle of a rifle barrel?
    i have watched various Utubes explaining how to crown the barrel either manually or in a lathe but I still don’t know what the ideal crown is or why it affects accuracy.
    al
    ps
    for most of 303s I own and shoot regularly, a bit better than 2” of accuracy seems the norm, say 1.5, generally best with 180 gn spire points, flat base and moderate loads of 2206H. My 303-25 sometimes appears to approach 1” but without very exact repeatable conditions, it’s a bit hard to tell. Reloading for me is a practicality not a passion. The 25 is a actually a fabulous caliber when loaded with 90gn projectiles. I have it sighted at 250m. As kangaroos tend to be a rather vertical target when standing (more like a ball when head down feeding) it gives the rifle an excellent effective range in field conditions. I wouldn’t feel disadvantaged with that rifle in any company with the shooting that presents itself at home in the Snowy Mountains of Australia.
    regards all
    al

  2. #2
    Join Date
    Mar 2010
    Posts
    2,456

    Default

    The crown is the last part of the barrel the bullet sees and if the crown is damaged or not concentric it will create gas jets that can affect the flight of the bullet. Having a perfectly concentric crown makes sure the gas vents all the way around the bullet evenly so the bullet isn't tipped or wobbled by the gas. Its pretty important and can make a huge difference in accuracy and group sizes if the rest of the rifle is up to it. For some rifles the crown is just the end of the barrel and even with a perfect crown you won't get any better accuracy. It all depends on a lot of parts working together.

    For top notch accuracy most of us cut the crown with the barrel set up in a lathe and dialed in to insure the bore is concentric with the center of the rotation. By using a boring bar to carefully cut the crown its possible to make it clean and concentric. Using piloted tools will work ok but the pilot sometimes causes issues at the one point where you can't afford any. Having the bore open up at all at the muzzle is a bad thing so high accuracy guys are generally against pilots on cutters for this. Once again though, you should fit the tool to the purpose. If you're just working on a milsurp shooter a piloted cutter is probably fine. If you're working on a rifle that usually shoots consistently less than half inch groups at 600yds pilots are bad.

    Hope that helps some. Its a loaded question with lots of answers and opinions as well. Kind of like the "how should I clean my rifle"and how often should I clean my rifle" questions.

    Frank
    Last edited by amafrank; 06-27-2020 at 09:44 AM.
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  3. #3
    Join Date
    Dec 1969
    Location
    New Zealand
    Posts
    4,301

    Default

    I probably re-crown a dozen or so rifles each week......we use a small piece of specially shaped and sharpened high speed steel for the job.In a lathe obviously.There is no ideal crown but you will never convince some people of that.The main thing is thats its even and concentric....we generally do a 60 degree crown unless the customer asks otherwise (which they hardly ever do unless its a really wide barrel) and this works quite well.....

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  5. #4
    Join Date
    Sep 2018
    Posts
    287

    Default

    Hi Amafrank,
    thank you for such an excellent, concise and understandable answer
    thanks also Caerlonie for your experience
    regards
    al

  6. #5
    Join Date
    Dec 1969
    Location
    michigan
    Posts
    1,362

    Default

    Crown shape makes no difference . The lands must be sharp and and the "Crown" square with the bore

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