Found something about .308 and 7.62mm. - The Firearms Forum

Mosin_Nagant_Fan · 11-10-2010, 03:46 PM

About a year ago I asked about ammo and how people get 7.62mm into .308in when .308in = 7.82mm (rounded the the nearest hundredth), only to get pretty much told off and no strait answer. After some research and calculating (both on the computer and by hand) I found that the ammo (bullet) IS .308in (7.82mm) in diameter but the bore on the gun is 7.62mm, at the lands (found out where the 7.62mm bit in the last sentence from Wikipedia).

Bindernut · 11-10-2010, 05:36 PM

Yup,
That's a typical difference in how the European and British cartridges are spec'd to the land diameter instead of the groove (or bullet) diameter out compared to the US method of bore size naming.

Similar examples...
The .303 British, which uses .311/.312" bullets
The 7x57 Mauser (called .275 Rigby in the UK) which uses .284" (7.21mm) bullets
The 8x57 Mauser uses .323" or 8.21mm bullets.

LDBennett · 11-11-2010, 06:36 AM

Cartridge names are virtually meaningless. Often the bore or grove diameter doesn't match anything in the name. Some names have historical connections like the black powder cartridges where the diameter and the amount of black powder is part of the name. Sometimes the name is made up as a sales gimmick.

So take no information from the name as to the size of the bullet or the grooves or the the bore or anything else. Refer to a good reloading manual for the actual dimension.

LDBennett

JLA · 11-11-2010, 07:47 PM

yup, thats whay a .300 win mag uses the same .308 caliber projectile as the .308 norma magnum, one cartridge is names for the groove diameter and one for the bore diameter

LDBennett · 11-12-2010, 06:52 AM

And some for neither groove or bore diameter!

11-10-2010, 03:46 PM	#1
Mosin_Nagant_Fan Advanced Senior Member Join Date: Jan 2007 Location: Montgomery, AL Posts: 1,832	Found something about .308 and 7.62mm. About a year ago I asked about ammo and how people get 7.62mm into .308in when .308in = 7.82mm (rounded the the nearest hundredth), only to get pretty much told off and no strait answer. After some research and calculating (both on the computer and by hand) I found that the ammo (bullet) IS .308in (7.82mm) in diameter but the bore on the gun is 7.62mm, at the lands (found out where the 7.62mm bit in the last sentence from Wikipedia). -->

11-10-2010, 05:36 PM	#2
Bindernut Advanced Senior Member Join Date: Oct 2007 Location: ND, USA Posts: 2,433	Re: Found something about .308 and 7.62mm. Yup, That's a typical difference in how the European and British cartridges are spec'd to the land diameter instead of the groove (or bullet) diameter out compared to the US method of bore size naming. Similar examples... The .303 British, which uses .311/.312" bullets The 7x57 Mauser (called .275 Rigby in the UK) which uses .284" (7.21mm) bullets The 8x57 Mauser uses .323" or 8.21mm bullets.

11-11-2010, 06:36 AM	#3
LDBennett Advanced Senior Member Join Date: Dec 2003 Location: Hesperia, CA Posts: 5,710	Re: Found something about .308 and 7.62mm. Cartridge names are virtually meaningless. Often the bore or grove diameter doesn't match anything in the name. Some names have historical connections like the black powder cartridges where the diameter and the amount of black powder is part of the name. Sometimes the name is made up as a sales gimmick. So take no information from the name as to the size of the bullet or the grooves or the the bore or anything else. Refer to a good reloading manual for the actual dimension. LDBennett

11-11-2010, 07:47 PM	#4
JLA TFF Moderator/Host Join Date: Feb 2007 Location: Heart Of Texas Contributor Posts: 17,305	Re: Found something about .308 and 7.62mm. yup, thats whay a .300 win mag uses the same .308 caliber projectile as the .308 norma magnum, one cartridge is names for the groove diameter and one for the bore diameter __________________ It takes 43 muscles to frown, 17 to smile, and 3 for proper trigger squeeze. The latest caliber or gear is no substitute for experience and skill. Rifles and cartridges don't make hits -- shooters do. Fact of life: After Monday and Tuesday, even the calendar says WTF!

11-12-2010, 06:52 AM	#5
LDBennett Advanced Senior Member Join Date: Dec 2003 Location: Hesperia, CA Posts: 5,710	Re: Found something about .308 and 7.62mm. And some for neither groove or bore diameter!