Cartridge dimension?

[aufevermike]

I am curious as to what the number after the "X" means. I know the first number is the caliber size and is general outside dimention of the bullet but what about the following?
Such as:
7.5 X "55"
7.62 X "39" or 7.62 X "54" what is the diference between the two, obviously the length has to do with it or is the circumference os the casing? or possibly the charge that the shell can hold?
or such a shell called the 30.06 what is the "06"

Sorry for the ignornace!

 

[The_Future]

I believe it's the length of the entire cartidge.

And the '06' of 30'06 is the yeah that it was relesed: 1906.

 

[CNYCacher]

As to the X number, I always thought that it was the length of something, either the entire cartridge (with bullet) or just the casing.

The 06 actually stands for the year 1906, which is the year the .30-06 was developed.
Pronounced "Springfield Thirty-ought-six"

I'm sure some better replies are on the way

 

[Freddymac]

Ignorance would be pretending to know, and not ask the question

in rounds like 7.62 X "39" or 7.62 X "54 the first number is the diameter in millimeters and the second is the length in millimeters. In the 30.06 or 30-06, the first number is the caliber in inches and the 06 is for the year 1906. although some older cartridges such as the 30-30 the second number is for the grains of black powder that the case held.
Please let us know if we can be of further assistance.

 

[Stickjockey]

In most modern cartridges, the second number is the case length in millimeters.

Freddymac: IIRC, the .30-30 was actually .30 caliber over 30 grains of smokeless powder. Others of the time, though, were in BP.

 

[Freddymac]

sorry...

you are indeed correct... I confuse that alot . My bad

 

[nfl1990]

And it would be said 7.62 by 39 kinda like 2x4 except diameter and lenth instead of width and height.

 

[dfaugh]

In MOST cases, the first number is the diameter (in mm) and the second is the case length (in mm).

But as pointed out, there are numerous exceptions...30-06 ('06 the year of introduction) or older cartirdges (30-30, .45-70, .25-55) where the second number was the original loading in grains of black powder. There may be a few other exceptions, that I can't think of right now.

Oh, just thought of a couple others: .22-250 and 7mm-08 (a 7mm bullet in a .308 case) or 8mm-06 (an 8mm bullet in a 30-06 case).

And, some are known by 2 names. For example .308 is also 7.62x51 NATO (although there are actually very slight differences). .223 is 5.56x45, again with very slight differences.

Confusing ain't it????

 

[AirForceShooter]

think lumber:

2x4

diameter X legnth

AFS

 

[unspellable]

2x4s and such.

And like a 2x4, the nominal dimensions and the actual dimensions often don't match.

 

[Jim K]

Just FYI, lumber dimensions refer to the unplaned dimensions; a 2x4 really is 2" by 4" when rough cut.

Yes, the second number refers to the case length in millimeters. The 7x57 and the like are commercial designations; military designtions vary. WWII German rifle ammunition was always called "7.9" by the German services; 8x57JS was the commercial nomenclature for the same cartridge.

The designation "JS" (Infanterie Spitzegeshoss) is pretty much unique to the German 8x57, but another letter can be very important and that is the "R" indicating a rimmed cartridge. Most of us know that 7.62x51 is the commercial designation for the 7.62 NATO, dimensionally the same as .308 Winchester.

But 7.62x51R is the .30-30, a different cartridge altogether.

Jim

 

[unspellable]

2x4

<< Just FYI, lumber dimensions refer to the unplaned dimensions; a 2x4 really is 2" by 4" when rough cut. >>

I've heard this many times. So why did the 2x4 go through several stages of reduction in size over the years? If all were 2x4 before planning then the amount they plane off has increased over the years.

In any case, its actual size is not the same as the nominal size which was my point. Many cartridges have designations that do not really correspnd to their size. 38 Special and 357 Mag both have a 357 bullet. 44 Special has a 429 bullet. 300 H&H, 30-06, 308, and 307 all have a 308 bullet. A 32 Special has a 320 bullet but a 32-20 has a 312 bullet. Etc. etc.

Bottom line is that any serious attempt to find ryhme or reason in cartridge designations can lead only to madness.