I've got a couple of questions here that I couldn't find on google. OK.

1)7.62x54 is a .308 and a 7.62x25 is a .308 and a 7.62x39 is considered a .310. WHY?

2)What does the x54, x25, and x39 mean? I know its a mm of some kind of the cartridge, but the measurement of what part?

# 7.62x54(.308), 7.62x25(.308), 7.62x39(.310)

Wed, 09/28/2005 - 11:05am

#1
7.62x54(.308), 7.62x25(.308), 7.62x39(.310)

1.) If you do the actual conversion from metric, 7.62mm

is 0.300", which happens to be about the bore diametre of

your average, garden-variety 0.308" barrel. I *think*

the original rifles chambered for 7.62x39 had somewhat

deeper grooves, being military and all, but the bore is

often nominally *close* to 0.300", thus it's also 7.62mm.

The metric designations *usually* reference nominal bore

diametre.

2.) The x54, x25, whatever, is case length in mm. There

may also be an "R" for rimmed cases, as in the 7.62x54,

which is, more specifically 7.62x54Rmm

breakopen308

I own a 7.62 X 54 and 3 - 7.62 X 39's. I am far from an expert on these cartridges but have always considered the "by" 54 pretty much equivalent to a .308 and the "by" 39 equivalent to a 30-30. I have seen the casings for a "by" 25 and it looks a tad larger than .22....... I'm sure someone will have the answer. I'm going to guess the 2nd number measures the diameter of the bullet in millimeters. The 1st number stumps me unless it might possibly be just a term to classify it as a military round?

Interesting topic and I'm looking forward to the answers we will hear.

still didn't answer either question.

1)Why would a 7.62x39 which is in between 7.62x54(.308) and 7.62x25(.308) be considered a .310

2)I already know that the second number is some sort of measurement but what exact part is the x54, x25, or x39 SPECIFICALLY referring too.

The last one refers to white_bass.

Hey thanks for the info so far Mossymo

white_bass

The "by" 25 case is significantly smaller than the other two rounds which it should be. But in relating numbers what I am saying is like 20 to 16 to 4.

Looking at a "by" 25 it seems to short of brass to make the 2nd numbers a measurement of the length of the cartridge case.

But as usual, I always reserve the right to be wrong !!!

Mossy,

25 millimeters is ~ 1". If you take a set of calipers and measure the

length of a 7.62x25 case, you'll get ~0.97-0.99". 7.62x54 case is

~2.1" long. Ain't metric fun? :-)

Todd

yeah, who's the idiots, the guys who created metric or the ones who decided not to use metric?!?!?

I found out from doing more research that the secondary # possibly refers to the case length like, white_bass said. No confirmation on that though yet.

Still not sure what makes the 7.62x39 a .310 instead of a .308 ???

ping

What we do in life echoes for eternity. Shadows and dust.

I had a customer come in yesterday and tell me that the x25 shoots a pistol round and the other 2 are rifle rounds. He reloads his own ammo. I got it confirmed that first is the diameter, and the second is the length. But he said that the x54 is considered more of a 30-06 than a 308, even though my ordering book for ammo shows the x54 at a 308. Still puzzling.

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