What is it about .30 / 7mm?

[A.J. Holst]

There seem to be a huge number of handgun and rifle rounds that fall in this size range.

Is it a "near" perfect diameter for flight? Easy / easier / cheaper to mfg than 6 mm or 8 mm?

Just curious....

[Caster]

I don't know. I don't care for either size. .35 caliber is where the magic is. You ain't lived until you've got into a .358 Winchester. By far my favorite center fire round.

[nightrunner]

I don't know of many popular handgun cartridges in either .284" (7mm) or .30cal. A couple of old outdated .30cal cartridges but nothing commonly used today.

For rifles, yeah. I think .30cal is just the old standard kind of like the Chevy small block and it just keeps on going.

7mm has good ballistic coefficients as does the 6.5mm which is growing in popularity among long range target shooters

[No_0ne]

Why .30 calibers?  Most likely because that was the standard military caliber that the US adopted for both World Wars. Since civilian weaponry tends to emulate that used by the armed forces, it became the de facto caliber for peacetime use as well.  Wildcatters, who did the initial development of many of today's calibers tend to start with cases and loads already in common usage and commercially available, thus the proliferation of .30 caliber cartridges ...

[A.J. Holst]

I don't know of many popular handgun cartridges in either .284" (7mm) or .30cal. A couple of old outdated .30cal cartridges but nothing commonly used today.

For rifles, yeah. I think .30cal is just the old standard kind of like the Chevy small block and it just keeps on going.

7mm has good ballistic coefficients as does the 6.5mm which is growing in popularity among long range target shooters

Sorry, I meant from .30 - .38 and 7mm - 7.7mm

[Jonnin]

its a good practical size for rifles for weapons of war.   If you look at the rifles in 30 caliber, the majority of them predate 1950 and were created for WW1, WW2, or some of the smaller conflicts of that era.   The number of 30 cal rounds developed since, say, 1980 are very few ...  300 blackout,  338 lapua, and not much else (might be one or two more, but compared to the 40 or so similar rounds in use by 1945...)

 

A part of it is going with what you know.   I have a rifle that shoots a round developed in the early 1890s that is virtually identical to the 308 in use today.  When something works, it makes sense to mimic it ....  we see that in the 357 sig, attempting to duplicate the performance of a specific load that was considered to be effective.   And the classic .. 30-06, guess what 06 stands for?   The round is over 100 years and going strong.

 

As for handgun rounds ...  the smaller 30 caliber rounds have largely fallen out of popularity.   9mm is .35 and is still your most popular choice  --- its the same diameter in 380, 38sp, 357 & sig, 9mm for one thing.  9mm is the compromise of choice to get a lot of capacity with a solid hit.   The 7mm 32 cal stuff is still in use for backup guns and pocket pistols but its not as common as it once was.   There is not a lot outside of these ... if you took away ALL the .32 cal and all the .35 cal (actual diameter of the rounds here) from the pool, there would not be much left --- its effectively variations of 5 or so cartridges (parent child cartridge evolution). 

Edited June 3, 2015 by Jonnin