- Mar 21, 2011
- Reaction score
- Northern Virginia
- Member of
- Private club on friend's land in Augusta County, Virginia
- USA (Colorado, Alabama, Virginia)
This has been covered ad naseum over the years in the gun rags...and probably on forums too. In a nutshell, for instance, the 270 Winchester bore starts out a bit under 7mm when the hole is drilled and it ends up right at 7mm - or about .276” - when the barrel grooves are cut and, therefore, utilizes what actually amounts to a 7mm bullet. On the other hand, the 7mm Mauser & 7mm Remington Magnum, for examples, start out with what amounts to a 7mm hole bored into the barrel and they end up right at .284” - which is really about 7.2 mm - when the grooves are cut and they, therefore, use bullets that are actually about 7.21 mm in diameter. 7mm is actually 0.2755906”...which is a lot closer to .277” than .284”...which is actually 7.2mm... but those giving cartridges their names don’t pay attention to any of that a lot of times.
Didn't know that. Very interesting. Thank you. Always thought the .284 was 7mm.