Originally posted by HoHun
Hi LJbomber,
>is a 303 a 7.9 mm?
1 inch = 25.4 mm
(That's the official definition :-)
So a 0.303" gun is a 7.70 mm gun. A 0.30" gun is a 7.62 mm gun.
(These might be nominal calibres, often the actual calibre deviates slightly. It's subject to a certain inaccuracy anyway.)
Regards,
Henning (HoHun)
Some semi-useless info:
Nominal bore diameter is what the caliber usually indicates.
For example, the M1906 (30-06) fires a bullet that measures.307-.309 inches diameter. Its replacement was the 7.62mm NATO round, which was the 308 Winchester with a FMJ bullet. Generally, the bullet diameter is .007-.009 larger in diameter than the nominal bore diameter. If it wasn't, it would not engage the rifling. If the bullet is of greater diameter than that described above, chamber pressures become too high. Excessive rifling engagement also increases friction, and thus bore wear is excessive (assuming you don't suffer an over-pressure related failure).
I believe that most .303 rounds used .311 diameter bullets.
The .303 used a rimmed shell casing, whereas the M1906 was classified as being rimless (uses an undercut groove for case extraction). You can push a .303 into a .30 rifle, but the bolt will not go home and you will likely break the extractor when it gets forced over the much larger diameter rim. Since the .303 uses a tapered bottleneck case, the case will wedge in the chamber of a .30 weapon and extracting it will be hard work.
Getting the M1906 round into a .303 chamber is equally difficult because the M1906 is considerably longer and will not allow the bolt to close.
My regards,
Widewing
