Why .30/7.62?

[raftman]

Kind of an odd question I've been thinking about. Is there a reason why so many rounds are .30 cal / 7.62? I mean, as far as rounds developed here in the US, there's .30-06 (7.62x63), .30 carbine (7.62x33), .30-30, .308 (7.62x51), .300 Win Mag (7.62x67) and probably others, but it's not just here, for example, the Russian calibers include 7.62x25 Tokarev, 7.62x38R Nagant, 7.62x54R, 7.62x39.

How and why did they arrive at that magic number? I know that all of these rounds don't literally have the exact same diameter and they aren't literally all exactly 7.62mm, but really, they're all close and the real diameters only often only differ by a few hundredths of an inch. Is there something about it that makes the dimension desirable?

 

[2afreedom]

I'm not a ballistics expert but my layman's guess is that somewhere around .30 caliber you get a bullet that is wide enough and heavy enough to reliably take the animals that most of us will ever hunt. Up until the .223/5.45x39 came along it also seemed to be the minimum caliber that was effective in battle. Sure a .45-70 will kill a deer but so will my .30-30 and it is a lot more comfortable to shoot. I think there's a similar phenomena with the .35/9mm caliber in handguns. They are both the minimum caliber considered effective for common uses.

 

[dawico]

When the military adopted the 30-40 Krag, they set the standard for American calibers. It wasn't the first .30 available, but the hunting community followed the lead. Then with the 30.03, 30.06, and the 308, they reinforced it. Surplus rifles made shooting and hunting more affordable to the common man, and why change? Now days, look at all of the .308 caliber bullets available to shooters and reloaders. If all of those military guns had been in another caliber, that would probably be the most common now.

 

[Crosshair]

I believe the primary reason was the fact that early smokeless powders combined with the steel available had problems with erosion. The smaller the bore, the greater the erosion after high round counts. Thus most countries settled on something around 30 caliber.

It also has to do with the fact that Spitzer bullets were not introduced until years later. RN bullets tend to not tumble, so you needed the larger bullet.

/Someone please correct me if I am wrong.

 

[aarondhgraham]

I think I know where .36 and .44 came from,,,

I read a book when I was a kid that said the reason the Colt percussion revolvers were made for those two ball sizes,,,
Was because the Navy used .36 caliber shot for their cannon loads,,,
And the Army used .44 caliber shot in their cannons.

Sam Colt simply designed the early revolvers to use a ball(s) that was already in widespread use by the groups he was trying to market his guns to.

I wonder if there was something already in use that prompted those early designers to choose .30 cal as a starting point?

.

 

[Lokpyrite]

That makes as much sense as anything else I've heard.