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Question What does Crowning do for a rifle, and how does one do it if you chop a barrel?

Discussion in 'Anything Airgun Related' started by Dag, May 30, 2015.

  1. Dag

    Dag Pro Poster

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    I realise that it appears to be an internal chamfer or recess at the muzzle but how crucial is it and what tools or methods do members use to achieve it?
    Having seen a couple of articles where it is mentioned it seems to vary between the very coarse use of a large drill bit and the precision use of a hone.
    Can anyone enlighten me please and do those who chop bits off barrels have any problems with crowning?
    Dag
     
  2. HEY HEY ITS HENDO

    HEY HEY ITS HENDO Active Member

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  3. mattyts

    mattyts Donator

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    You can do it a number of ways, either by cutting, on a lathe or grinding, either with a proper stone or bit, or by making your own I've seen people use a dome headed screw in a drill with valve grinding paste.

    It let's the projectile and propellant leave the barrel evenly, and gets rid of any burrs left from cutting.
     
  4. meerkat1

    meerkat1 Keyboard Hero

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    i used a countersink bit seemed to work fine the rifle was still accurate
     
  5. Jackroadkill

    Jackroadkill Donator

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    Have seen a few methods; the ones that stick in my mind are a brass crowning tool (looks a bit like a countersink) and a ball bearing and grinding paste. Have never had any reason to try either of them but no doubt will have a go at some point or other.
     
  6. Stevie Darling

    Stevie Darling Sexual tyrannosaurus

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    Isn't to make smooth transition when the pellet exits the barrel??:)
     
  7. David M

    David M Donator

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    I carbined my springer a few years back the belt and braces method of plugging the barrel with wadding then hacksaw, fine file and set square, then recrowned it using a 10mm dremel grinding ball in a hand drill with fine grinding paste. Whilst turning the drill's handle I rotated the drill's grip in the opposite direction of the bit in circles of about 6". Fairly easy with care and left the gun as accurate as before. I set out doing it to make the rifle more manageable with one of Matt's superb silencers on, BUT, carbining it made a lot louder mussel crack and the silencer then made it sound a bit like it did unsilenced before I cut it about..! I wouldn't have bothered if I'd realized beforehand.....:up:
     
  8. terry1001

    terry1001 Major Poster

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    Crowning is intended to protect the end of the bore from damage and usually takes the form of a recess. It is thought important that the end of the bore is perfectly even so that the projectile leaves the barrel totally aligned with the bore and that the end of the bore is perpendicular to the axis, if it isn't the propellant gases will escape on one side before the other and cause the projectile to be deflected from its natural course.
    When making the crown the important thing is to get it concentric with the bore so the preferred method is to produce it on a lathe with the barrel set up so that the bore is running true, not the outside of the barrel. If there is some slight damage to an existing crown it can probably be polished out but anything more than that would require it to be re-cut from scratch, likely causes include wear from cleaning rods inserted from the muzzle etc although most rods are much softer than the steel of the barrel. Trying to make a new crown using hand tools is likely to be difficult and may make the problem much worse rather than curing it.
     
  9. Dag

    Dag Pro Poster

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    Very interesting and thanks for the link. Looking on the internet this evening there seem to be a number of articles which concur with the one above and whilst some folk would argue precision turning is necessary there are many others who advocate hand crowning with, as Matty has mentioned, the simplest and cheapest of equipment. I can see rhe argument for clean and symmetrical exit of gas or air but the shape of the crowning seems just as important inasmuch as some barrel muzzles have obviously been recessed rather than just chamfered or finished with a radius.
    Thanks for all the replies and suggestions.
    Dag
    See also: http://www.thehighroad.org/archive/index.php/t-625029.html
     
  10. oliver13

    oliver13 Donator

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    I've done it with a big brass roundhead screw & grinding paste, it was a bit of a long drawn out process, even mounted in a drill. I think if I do it again I'll try some kind of countersunk bit.
     
  11. oliver13

    oliver13 Donator

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    I've done it with a big brass roundhead screw & grinding paste, it was a bit of a long drawn out process, even mounted in a drill. I think if I do it again I'll try some kind of countersunk bit.
     

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