The Accurate Reloading Forums THE ACCURATE RELOADING.COM FORUMS Guns, Politics, Gunsmithing & Reloading Gunsmithing mm's vs. actual diameter?Go | New | Find | Notify | Tools | Reply | |
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Can someone explain to me why the bullets for 6mm, 6.5mm, 7mm, and 7.62mm (I didn't figure beyond that) are approximately .008 (8 thousandths) oversize to their actual mm designation? xxxxxxxxxx When considering US based operations of guides/outfitters, check and see if they are NRA members. If not, why support someone who doesn't support us? Consider spending your money elsewhere. NEVER, EVER book a hunt with BLAIR WORLDWIDE HUNTING or JEFF BLAIR. I have come to understand that in hunting, the goal is not the goal but the process. | ||
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Wouldn't that be about the difference between the bore and the groove? _______________________________________________________________________________ This is my rifle, there are many like it but this one is mine. My rifle is my best friend, it is my life. | |||
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 Probably the same reason a 25 cal. is .257",a 27cal is .277" a 30 cal. is .308" a 33 cal is .338" a 35cal is .357" or .358" etc.Westpac had it.  rogerOld age is a high price to pay for maturity!!! Some never pay and some pay and never reap the reward. Wisdom comes with age! Sometimes age comes alone.. | |||
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European cartridges have traditionally been designated by the land-to-land measurement (bore) while American cartridges are more often designated by the groove-to-groove measurement (equal to bullet diameter). A 6.5mm bore is .256" (like the .256 Mannlicher cartridge), and uses the same diameter bulet as a .264 Winchester (.264"). There are exceptions: The .270 Winchester is named for its bore. If it were named for its bullet, it would be a .277 Winchester. 7mm bores are .276", while the bullet is .284. The experimental .276 Pedersen is an example of an inch name using bore rather than bullet diameter. | |||
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Yes., As mentioned above many European "mm" designations refer to the bore (land) diameter, rather than groove diameter. An example is the so-called "8mm Mauser". The ones that were supposed t fire .318" diameter bullets were originally given the civilian designation of 7,8mm. this would be .3115" in diameter, so if rifled with a groove diameter .004" over that, would be have a groove diameter of .3195. But since the Germans usually cut their grooves .005" deep, for a total of .010, the actual groove diameter of these rifles was .3215"-.322". So if you used groove dai. for caliber designation, they would have been called an 8,2mm........... "Bitte, trinks du nicht das Wasser. Dahin haben die Kuhen gesheissen." | |||
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Glad you asked the question as this is a great thread for a rookie like me... I've learned alot here from the replies...  Thanks! | |||
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depends on whether the m&m's are plain or peanut   (its friday - I'm allowed) | |||
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