How was it coincidentally that all major countries simulataneously developed different main battle rifle cartridges that were all essentially 30 cal? The same question goes for the 6.5mm.  

Just a ramblin thought.

Jeff

N.A.T.O. We forced the 308 on most of our allies during the cold war. Then we forced the 5.56 on them,then turnabout being good fun. They forced the 9mm on us.

A major consideration of caliber is what is required to kill a horse.  This from the mounted cavalry days.  Remained a consideration until horse-drawn artillery caissons (sp?) were obsoleted during War2.

I believe the .30 came into the game with the .30-03 cartridge, so Hatcher probably had something to do with it.  Or was it the Krag?  Anyway...

When killing a horse was no longer a requisite, ie. post-War2, smaller calibers became feasible.

I am not referring to Nato standardizing and rounds.  I am talking about how every country independantly designed cartridges which all someone had the same caliber ie: 30-06, 8mm Mauser, 303 British, 7.62X54R, 8mm Lebel, and 30-40 Krag.  All different countries but all within the low 30 (.303 to .314).  It strikes me as odd that none of the Major turn of the century powers developed anything but 30s for their service rifles.  

They did try smaller and larger cal.The 6mm, 6.5's, 7.9's and a few 40's. But they saw that the 30's seemed to work better. You have to remember most were just changing over from blackpowder and the then new 7mm and 8mm's from Germany seemed almost too good to be true.Some think we just split the diff. between the two and made the 30's.

England and France were among the first to adopt small bore service cartridges.  France developed smokeless powder in 1888 and adoopted the 8mm Lebel in, I believe, 1889.  England introduced the .303 Mk1 cartridge in Feb., 1889 using 71.5 gr of compressed Black Powder!  Previously, the most ballisticaly efficient cartridge produced was the 9.5x60R Mauser cartridge.  It was introduced in 1887.  It produced about 1700 fps with a lead, flat point bullet.  France & England wanted flatter trajectories than their current BP cartidges  allowed and experiemnted with RN & even spitzer bullets before adopting their new service rounds.  The bore sizes they chose were a balance of power & fouling.  To get a flatter trajectory, the bullet had to go faster but faster bullets fouled the bore badly.  Cupro-nickel cladding was developed and used for a while.  It solved the problem of leading but was itself difficult to remove.  Later, the so called guilding metal (Cu & Zn) now used was developed.  The bore sizes seemed to be a national preference.  France and Gemany adopted 8mm while England and the US (in 1892, the .30 Army or .30-40 as we know it), Belgium, Russia and Switzerland went to the .30 cal (more or less).  Others, like Spain & much of South America went to the 7mm; still more went to the 6.5mm (Norway, Italy, Japan, etc.)  There was a long development and perfection of cartridge design that encompassed the powder formulea, powder additives, jacket material, primer compounds, barrel steel, bullet design & cleaning compounds.

The Horse idea is why the 45-70 was developed, in the indian wars contray to what the movies show, most of the time the horse was the target of the cav or infantry trooper. Distroy the horse and the planes indian had no mobilty and most could not fight effectivly when afoot. The French developed the 8mm label, it was the first smokeless military round. The rest of the world scrambled to catch up. The Brits where starting to use the .303 Lee-Metfield and looked for a idea for a small bore smokeless load, the Lee-Enfield was the result. Then other countrys got into the small bore act 6.5 up to 8mm seemed to work best in the bolt actions used as main battle rifles worked best with bottle necked rounds, and the MGs coming into use also worked well with them. Remember the 8mm label was first, every body else just kind of followed suit. Some is history some is just my opinion.  

Actually, the U.S. was first in smaller cartridges with the 6mm Lee Navy, in 1895.  I
believe politics ruled with the 7.62 Nato (308)
John