turning a 6mm blank

[sandyn]

I'm having a problem finding a barrel blank in 6mm at least 26 inches long that weighs under 4 pounds. I need to make weight in the 10.5 class. I need a 7.5 to one twist also. Why can't I buy a fatter blank and have it turned so that the muzzle is around .67 or somewhere in that area, so that it falls under 4 pounds. Its only a blank, it would just heat up faster, wouldn't it?
thanks
sandy

 

[LHSmith]

When you reduce the OD of a barrel the ID will actually increase.....perhaps ten thousandths or more ......but enough to MAYBE reduce it's potential (accuracy-wise)
In addition you will induce stress on the barrel, which having it cryo'd MAY help relieve. Bottom line- you're gambling a lot of $$$ on a barrel that MIGHT work to your satisfaction.... but the ODDS are that it WILL give you frustration, especially if used in competition.

 

[Eddie Harren]

Have you checked out a Medium Palma contour?

 

[wapiti25]

LHSMITH, you should proof read your posts. You say that the bore will grow "ten thousandths", do you know how much ten thousandths of an inch is? That I think is an error in your typing. Barrels are a cylinder piece of steel that is drilled and rifled then it may be turned to a conture that most of us buy. Some barrel makers lap the bore after turning but not all. I see people use .001 instead of .0001 before on the site and that is a ten times error. you said "ten thousandths" (.010) when I hope you ment to say a tenth of a thousandth (.0001) which is a hundred times smaller. Because a bore grows .0001 or .0002 does not automatically say it will not shoot good. In the 6mm barrels some like the bore, not the groove, to be .236 or .237 and that is a whole thousandth of an inch. To answer the original question I would see if the barrel maker will turn a larger blank down as it may be cheaper than the price a gunsmith will charge. All barrels do not shoot the same from the same maker or we all would be buying from one maker. We tend to look to see which barrel maker's barrel has been winning the matches. I may have said too much, if so I apologize. good luck with your build.

 

[Obtunded]

Light palma cut to length, or a Kreiger # 4 contour will all give you what you need.

 

[LHSmith]

Yes, I meant to say "perhaps 0.0001" or more".
Depending on the barrel make, it may be properly stress-relieved to avoid this dimensional change. If not, and your turning to a taper, you'll end up with the muzzle at a larger diameter than the chamber end....this would not be a good thing. I assume the top makers like Kreiger and Bartlein run their air gauge tests for uniformity in the barrels final configuration. A barrel that has dimensional uniformity through it's entire length is what's most important....and you may loose that guarantee unless your Smith air gauges the barrel after contouring.

 

[tdking]

Krieger makes cut rifled barrels and contours the blank BEFORE rifling. This is not possible with a button rifled blank. This is also why Krieger is one of the most popular and best shooting barrels available. The bore dimension is consistently uniform. Krieger also laps their barrels after reaming to smooth the bore prior to rifling, then again after rifling. Check their web site and you can read about it for yourself.

Theron