Around the turn of the century say from mid to late 1880s through about 1910 most of the major belligerents of WWI and WWII had adopted cartridges that were essentially in the thirty caliber category. Two exceptions were the Japanese with the Arisaka rifle in 6.5x50mm and the Italian Carcano rifle in 6.5x52mm. Though the Japanese were in the process of switching to 7.7x58mm which is essentially a rimless .303 British.
How do we define “essentially thirty-caliber?” Well look at this list table.
Cartridge – Country of Origin – Bullet Diameter – Notes
.303 British (7.7x56mmR) – UK – 0.312”/7.92mm – Introduced: 1889 WW2: 175 gr Spitzer Boat Tail
7.62x54mmR Russian – Russia – 0.312”/7.92mm – Introduced: 1891 WW2: 148 gr (Flat Base?)
30-06 (7.62x63mm) – US – 0.308”/7.8mm – Introduced: 1906 WW2: 150 gr Spitzer Flat Base (M2) Current: 174 gr Spitzer Boat Tail
7.9x57mm Mauser – Germany – 0.324”/8.22mm – Introduced: 1905 WW2: 197.5 gr Spitzer Boat Tail
The bullets diameter is the actual diameter where the actual bore diameter is about 0.008 smaller, hence the US .308” is a 30 caliber bore across the lands. Groove diameter means the bullet is bigger than the bore to swage the bullet and engage the rifling to obtain obturation (sealing of bullet to the bore to prevent expanding gases to escape). Rifling spins and stabilizes the bullet while the over bore bullet engages the rifling.
Boat Tail Bullets
Boat tail bullets where discovered during WWI and became pretty much the standard design as they carried further and offered a higher ballistic coefficient than the standard flat base bullet. The large weight bullets were fired at lower muzzle velocities, while the lighter bullet was a little faster, but less recoil. It all boils down to a rough equivalency across the board. The 30-06 is at the low end for bullet diameter, while the Mauser reigns at the high end. But the effect was very similar across the board on the bullet’s arrival at the target.
Round Nose Bullets & Minie Balls
Prior to the arrival of smokeless powders, a similar comparison of cartridges would yield similar designs for black powder military cartridges all falling close to the .45 caliber. All the rifled muzzle loaders pretty much stuck to the prevalent 50+ caliber. Oh, the details change with powder capacity and cartridge profile, but the bullets were usually round nose, and the Minié Balls for muzzle loaders were close to the same worldwide.
Modern Artillery Guns
Of course, there are similarities in heavier ordinance. Take the prevalence of 75mm to 78.2mm, i.e. 3” guns and howitzer, seems like everyone had a 3”. Medium howitzers stuck to the 5” bore (150,152 and 155mm) were common. Navy all had 115mm to 130mm or 6” guns. It is interesting how quickly friends, neighbors and potential adversaries all jump on the band wagon when it comes to adopting ordinance. Today the Western nations all use 5.56mm rifles, 7.62mm medium and about .50 caliber heavy machine gun and sniper calibers. NATO has 105 and 155mm howitzer while all the former Warsaw Pact have the 152mm. Leave it to the Russians to toss in 122mm artillery, more of a gun-howitzer. All western countries have the 105mm (former) and the 120mm (current) tank guns. It goes on to similarities in aircraft guns and other areas. The point is when some nation finds something that works there is a scramble to match it and don’t matter if you’re a ‘cannon cocker’ or an infantryman.
International Military Cartridge Comparisons
The thirty caliber is the de facto standard of comparison in the US. The standard was the 30-06, but today we compare everything to the 7.62x51mm/308 Winchester. However, every cartridge has it merits. The 308 can match the 30-06 up to around 150 grain bullets. But the extra case capacity makes the 30-06 able to handle the heavier bullets above about 175 grains on up. And if you’re a varmint hunter the thirties are way too much. And you would want something with a little more in the boiler room when facing a cape buffalo or elephant. But international military cartridge comparisons are at least interesting.
Shooting Range Industries