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Barrel flute timing?

 
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  #8  
Old 10-02-2013, 06:57 AM
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Location: Texas
Posts: 5,384
Re: Barrel flute timing?

Quote:
Originally Posted by MontanaRifleman View Post
Yup, that is what I'm talking about

If you look at the barrel makers acceptance criteria he will have an end to end tolerance.

Most premium barrels that I use are guaranteed to be uniform dimensionally to within .0001
and .0002 for Chrome Molly barrels. contours can be off on the outside by .000 to .005 (Industry
standard acceptance)from end to end. Any more than this should be rejected and sent back to the barrel maker.

I have had premium barrels go as high as .014 end to end and sent them back with no problems.

Some factory barrels have had to be re-contoured to true them up. most are bore straightened
after all work is done leaving the outside with run out because it was contoured while the bore
was still as drilled and rifled.

My preferred barrel makers barrels are normally .0000 to .0015 max.

I have heard of this Barrel orientation thing because of barrels not being straight, but have never
kept one that needed any special orientation due to being crooked/bent.

So , If the barrel is straight and true to the bore , there is no special requirement for orientation.

Some barrel manufacturers tolerances are more generous and may go up as high as .005 to .007
and I just prefer not to use them.

In My opinion : If you have to do something special to a barrel because of it's straightness it needs
to be rejected and sent back.

J E CUSTOM
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  #9  
Old 10-02-2013, 07:09 AM
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Re: Barrel flute timing?

Quote:
Originally Posted by IdahoCTD View Post
All bores are curved. They are turned on centers but some are like a jump rope between the two ends and some are out very little. He is talking about timing the curve of the bore into the vertical plane weather it is pointed up or down. If you have a long stem indicator you can dial a barrel in with the indicator in as far as it will go and then pull it out a inch or so and dial it in there as well. Basically your going in and out until that 1" section runs as true as you can make it. Then you run a indicator on the opposite end of the barrel to find the run out or "high spot". In theory this makes the point where the bullet enters the rifling as straight as possible to the bore.
+1 to JEs post. If you have to do special 'orienting' to a barrel you need to send it back. You are living too much in the world of theory!
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  #10  
Old 10-02-2013, 07:55 AM
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Location: Tulsa
Posts: 1,004
Re: Barrel flute timing?

I see this discussed frequently. There are two ways, that I know of, to dial in a barrel through the headstock. One of these methods will likely leave the need to clock the muzzle. That method seems to be the one most commonly used.

Maybe You and JE could describe how you dial in a barrel blank before chambering.
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  #11  
Old 10-02-2013, 08:44 AM
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Posts: 796
Re: Barrel flute timing?

Typically barrels all fall within the specifications you gave JE even though the bore curves. Even if you cut them down the bore still is within the .005" tolerance you gave. I have seen a few way off yet they still shoot. This video explains things better than I will typing. Try it next time you dial a barrel in, if you have a long stem indicator, and see how far off the back end is.


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  #12  
Old 10-02-2013, 08:49 AM
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Location: South of Canada and North of Wyoming
Posts: 5,954
Re: Barrel flute timing?

Quote:
Originally Posted by J E Custom View Post
If you look at the barrel makers acceptance criteria he will have an end to end tolerance.

Most premium barrels that I use are guaranteed to be uniform dimensionally to within .0001
and .0002 for Chrome Molly barrels. contours can be off on the outside by .000 to .005 (Industry
standard acceptance)from end to end. Any more than this should be rejected and sent back to the barrel maker.

I have had premium barrels go as high as .014 end to end and sent them back with no problems.

Some factory barrels have had to be re-contoured to true them up. most are bore straightened
after all work is done leaving the outside with run out because it was contoured while the bore
was still as drilled and rifled.

My preferred barrel makers barrels are normally .0000 to .0015 max.

I have heard of this Barrel orientation thing because of barrels not being straight, but have never
kept one that needed any special orientation due to being crooked/bent.

So , If the barrel is straight and true to the bore , there is no special requirement for orientation.

Some barrel manufacturers tolerances are more generous and may go up as high as .005 to .007
and I just prefer not to use them.

In My opinion : If you have to do something special to a barrel because of it's straightness it needs
to be rejected and sent back.

J E CUSTOM
Interesting, the smith who recently did my 300 RUM, with Broughton barrel, said that he checks for the barrel's runout and times it so that it is either pointing up or down and not side to side. He is a very experienced and reputable smith. I guess there are 2 schools of thought on that. I thought he was talking in the thou range, maybe he was talking in the tenth of thou range?
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  #13  
Old 10-02-2013, 08:50 AM
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Re: Barrel flute timing?

Here is another good video to help explain.

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  #14  
Old 10-02-2013, 10:43 AM
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Location: North Bend, Oregon
Posts: 1,201
Re: Barrel flute timing?

Just like these two video's, I dial in the bore of the end I am working on. If its the chamber end I dial the throat and then 2" farther in. Once dialed in the other end is frequently running out .005" to .040" and as much as .080". Very rarely do we see one running less than .010". I run an indicator on it to find where the barrel points up. I never point them down. If we overclock we take it around another turn to get it to point up. I then split the difference to orientate the flutes properly. This may have the curve pointing just slightly left or right but not by much. If I were to ignore the flutes it would make for a very bad appearance and will not ever orientate the flutes with a flute at the stock line. It looks terrible. You can have good looks and shoot.
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