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What difference does the groove count make in a barrel?

 
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  #1  
Old 08-05-2009, 01:49 PM
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What difference does the groove count make in a barrel?

It's just a matter of time before I shoot the barrel out of my 6mm284. I am looking ahead to replacement and am thinking about buying a Pac-Nor. They list 3,4,5,& 6 groove barrels, as well as polygonal.

Can someone explain the benefits/drawbacks of the various groove options to me?
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Old 08-05-2009, 03:36 PM
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Re: What difference does the groove count make in a barrel?

IMHO, 3 groove barrels are much better for barrel burners such as the 6mmx284. This is because the lands are twice the width of the lands on a 6 groove (at least on Lilja barrels, I dont know about PN barrels). This will hold up under the heat a bit better than a narrow land which will save the throat area a bit. It isnt a cure all but can add a few usefull shots to the life of the barrel. Maybe 10-20% ish.
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Old 08-05-2009, 04:03 PM
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Re: What difference does the groove count make in a barrel?

Although I agree with Michael that wider lands stand to last longer than narrower lands, there is a potential downside of wide lands, especially for overbore cartridges like the 6mm-284.

Kirby Allen explained this one time as 'Bearing Surface Compression' (BSC). The idea is that wider lands compress a greater percentage of the bullet's circumference, putting more abuse (heat/friction) on the bullet. Kirby uses the percentage of BSC as an indicator of how likely a bullet is to survive when fired from an overbore cartridge. (Kirby, please step in here and correct me if I'm misrepresenting your ideas).

So wide lands may stand to add life to your barrel, but they may be more likely to end life for your bullets. Of course if you're not dealing with an overbore cartridge and bullet failure is not a consideration, then you'll have the longevity advantages of the wide lands without the downside of bullet failure.

Take care,
-Bryan
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Old 08-05-2009, 04:27 PM
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Re: What difference does the groove count make in a barrel?

My gun was one that Kirby was involved with when the testing of the width of lands/grooves was going on. I had a 3 groove Lilja and we finally pulled the barrel and sent it to Lilja for inspection and testing and it came back with a clean bill of health and a video tape of the testing, although it was destroying bullets.

Kirby did extensive testing and evaluation and as a test he had Mike Rock build some barrels to his specifications as far as lands and groove width goes and I now have a 5 groove Rock built to Kirby's specs and it's happily spitting anything I feed it out the tube and down range.

I agree with the performace level of the round vs. the 3 groove barrel and it's advantages but.....since I prefer a little more horsepower, I'll stick with the barrels configurations that fit within the guidlelines of what Kirby came up with.
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Old 08-05-2009, 04:28 PM
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Re: What difference does the groove count make in a barrel?

Thanks Bryan. You may have saved me from a huge mistake. I appreciate you taking time to respond to my question. Good work you have going on at Berger too.

Was Kirby's theory on BSC posted on this site?
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Old 08-05-2009, 04:32 PM
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Re: What difference does the groove count make in a barrel?

Quote:
Originally Posted by cornstalker View Post
Was Kirby's theory on BSC posted on this site?
Check out this thread and see if it helps. Link--> 3 groove Barrels
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Old 08-05-2009, 05:07 PM
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Re: What difference does the groove count make in a barrel?

That is a tremendous help ss7mm!!

Thanks for the link, I have my answer.
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