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We in the USA tend to measure bore diameter across the lands. The Europeans/Eastern bloc measure across the grooves. Trying to make sense of cartridge naming is an exercise in futility. The .44 Mag uses a .429 bullet while the .41 Mag uses a .410 bullet. The .38 Special uses a .358 bullet so it would more appropriately be called a .36 Special?
 

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http://mdmetric.com/tech/cvtcht.htm/

i thought a 7.62 x 51 = .308 cal.
7.62 x 39 = .311 cal
7.62 x 54r = .311 cal.

the above conversion makes 7.62mm = .300 cal.
neither .308, or .311 = 7.62mm
Unfortunately there is no standard. We still have the .45-70, and the .250-3000.

I've learned the system, but I gave up trying to understand it years ago!:D
 

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do NOT assume that the system makes sense. Much of the naming was done by marketing departments after a 3 martini lunch. .50 Browning Machine Gun is NOT .50 inches in diameter. There are a handful of 9mms - many of which are NOT 9mm. .32 Short Colt and .32 S&W are not the same diameter. Neither is .22 LR and .22 Magnum. And yes, Americans measure a bore one way, Europeans another.

Why ask why? Drink Bud Dry. :p
 

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Lazzaroni has the most accurate MM designation. Their 7.82 Warbird is an honest .308 diameter. .308 divided by .03937 = 7.82 MM.
 

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Lazzaroni has the most accurate MM designation. Their 7.82 Warbird is an honest .308 diameter. .308 divided by .03937 = 7.82 MM.
But is that measurement taken from the lands or the groover??:D:p:D
 

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But is that measurement taken from the lands or the groover??:D:p:D
The 7.82 Warbird represents the bullet diameter of the round, which is .308.
 

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In that case, it should be the sdame diameter as the grooves.:p

BTW, I was pulling your leg with the last post!:D:D
 

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In that case, it should be the sdame diameter as the grooves.:p

BTW, I was pulling your leg with the last post!:D:D
Which grooves? The ones in the barrel, or the ones on the bullet after it comes out??? :D
 

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c3shooter said:
do NOT assume that the system makes sense. Much of the naming was done by marketing departments after a 3 martini lunch. .50 Browning Machine Gun is NOT .50 inches in diameter. There are a handful of 9mms - many of which are NOT 9mm. .32 Short Colt and .32 S&W are not the same diameter. Neither is .22 LR and .22 Magnum. And yes, Americans measure a bore one way, Europeans another.

Why ask why? Drink Bud Dry. :p
Hum the 50 bmg is. 502" in dial. How is that not 1/2"?
 

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Actually, an UNFIRED .50 BMG has a max diameter of .510. On firing it is squeezed to .50.
 

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Get a good reloading manual by Lyman, Speer or Hornady, it will

solve a lot of mysteries for you. Case in point:

The .45 ACP vs .44 Rem Mag comparison-

I shoot my .44 through one BBQ tank and make a

massive dent on the next one, while a .45 only makes

a dent on the first one.

The manual points out that the .44 uses @ 5 times as much

powder.
 

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Discussion Starter #18
Actually, an UNFIRED .50 BMG has a max diameter of .510. On firing it is squeezed to .50.
wrong..........straight from a .50bmg barrel maker

We make our .50 caliber barrels with a .500" diameter bore diameter and a .510" groove diameter. The twist rate options are 15" (for the 50 BMG cartridge) and 32" and 48" (for black powder guns and limited to 30" finish length).
 

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See can`t none of ya make up your minds, told you it will drive you crazieeeeeeeeeeeeee.
 
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