6mm bore diameter?

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pyscodog

Active member
I see 6mm barrels for sale and someone always asks, is it a .236 or a .237 bore. Being only .001 difference, whats the difference? Why would one prefer one over the other? I realize the .236 is tighter, thats not the answer I'm looking for.
 
In the past taller lands worked better with cast bullets, I have a 9.3 with a groove diameter of .364 and a bore diameter of .344 circa 1907.

To get the true answer just call the barrel maker with the tallest lands and ask them "Why".
 
Ok, I'll take a guess.

It's a bench rest thing. The .236" Bore is the standard 6mm bore size that you'll find on factory rifles, not the .237". A 6mm bore is actually .23622", at least in theory.

The .237 bores have become more popular in short range/point blank BR. They supposedly cause less bullet distortion while providing adequate engraving on a 6MM bullet to make a legitimate difference in group sizes. Also, BR shooters worry about 6MM bullet diameters too.

In a normal 6MM factory rifle, you might get anything in between .236" and .237"(hopefully), so it won't make any difference for practical purposes if you're just ordering a new barrel for your deer slayer.
 
Thanks Winny,much better answer. I honestly didn't know the difference but see it ask quite often on Accurate Shooter. The BR guys hang out there so I guess its important to them. Not so much to an old redneck like me.
 


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