.308 vs. 7.62x51

[MMH]

I Heard that rifles chambered for 7.62x51 should not shoot .308 Win. Confirmed this by reviewing SAAMI spec - the allowable pressures for .308 are 62,000 psi & the allowable pressures for 7.62x51 are 50,000 psi. The opposite of .223 vs. 5.56x45. So, when shooting FALs, M1As, AR-10s - should .308 Win not be used?

[wjkuleck]

Originally Posted by MMH

I Heard that rifles chambered for 7.62x51 should not shoot .308 Win. Confirmed this by reviewing SAAMI spec - the allowable pressures for .308 are 62,000 psi & the allowable pressures for 7.62x51 are 50,000 psi. The opposite of .223 vs. 5.56x45. So, when shooting FALs, M1As, AR-10s - should .308 Win not be used?

Sigh.

You are comparing apples and kumquats. SAAMI specs are in Piezo-measured psi, military, in crusher-measured CUP (Copper Units of Pressure). There is no meaningful nor practical way to correlate the two measurement systems.

The difference in cartridges, whether dimension or performance, are negligible, if any. The only consideration is whether your rifle has a "long" military chamber, e.g., the USGI military chamber. Unless you have one of the 50 or so M14s in private hands, or one of the few thousand 7.62-MM "Navy" Garands, you'll not see a USGI 7.62-MM military chamber in a US-made rifle.

Check the headspace; if it falls within .308 Winchester specifications, you're good to go. M1As, Fulton ARmory M14s and Titan UPRs, other AR-type .308s are all chambered for .308 Winchester dimensions.

I have two "7.62-MM" marked rifles. One, an Ishapore 2A, has a "long" military chamber (the bolt closes on .308 NO-GO, though not on FIELD). I will use only cartridges with military brass in order to stand the gaff. My Sterling-converted 7.62-MM No 4 Mk 1*, on the other hand, is .308-Winchester headspaced.

Note that we have never found a 7.62-MM (that's the US Army way of saying "7.62x51mm 'NATO'") cartridge that did not fall within .308 Winchester SAAMI dimensions, so the .308 chambers found in Fulton Armory rifles and M1As and the like accept 7.62-MM cartridges just fine.

One of my correspondents has written a marvelous FAQ article which will be up on the Fulton Armory FAQ Page in due course.

Watch out for those apples and kumquats .

Regards,

Walt

[daschnoz]

[wjkuleck]

Originally Posted by daschnoz

Hey, 50 years ago I had my hair just like that!

As it is said in the Navy, "There's always somebody who doesn't get the word."

Regards,

Walt

[DaveM55]

Originally Posted by wjkuleck

Hey, 50 years ago I had my hair just like that!

As it is said in the Navy, "There's always somebody who doesn't get the word."

Regards,

Walt

Turn two...commence ships work...Have a fine Navy day

[MMH]

Originally Posted by wjkuleck

Sigh.

You are comparing apples and kumquats SAAMI specs are in Piezo-measured psi, military, in crusher-measured CUP (Copper Units of Pressure). There is no meaningful nor practical way to correlate the two measurement systems.

The difference in cartridges, whether dimension or performance, are negligible, if any The only consideration is whether your rifle has a "long" military chamber, e.g., the USGI military chamber. Unless you have one of the 50 or so M14s in private hands, or one of the few thousand 7.62-MM "Navy" Garands, you'll not see a USGI 7.62-MM military chamber in a US-made rifle.

Check the headspace; if it falls within .308 Winchester specifications, you're good to go. M1As, Fulton ARmory M14s and Titan UPRs, other AR-type .308s are all chambered for .308 Winchester dimensions.

I have two "7.62-MM" marked rifles. One, an Ishapore 2A, has a "long" military chamber (the bolt closes on .308 NO-GO, though not on FIELD). I will use only cartridges with military brass in order to stand the gaff. My Sterling-converted 7.62-MM No 4 Mk 1*, on the other hand, is .308-Winchester headspaced.

Note that we have never found a 7.62-MM (that's the US Army way of saying "7.62x51mm 'NATO'") cartridge that did not fall within .308 Winchester SAAMI dimensions, so the .308 chambers found in Fulton Armory rifles and M1As and the like accept 7.62-MM cartridges just fine.

One of my correspondents has written a marvelous FAQ article which will be up on the Fulton Armory FAQ Page in due course.

Watch out for those apples and kumquats .

Regards,

Walt

Apples and kumquats? Maybe. I am familiar w/ piezzo measured pressure & CUP measured pressure. In addition, the pressure is measured at different locations. Bottom line, no correlation is possible between the two methods. Has anybody tested .308 Win w/ a CUP type of test? Also, I have not scrutinized all chamber dimensions to compare .308 Win to 7.62x51. I know that the headspace tolerance is different, but that there is enough overlap where a rifle can be headspaced such that it meets both SAAMI & NATO.

Apparently I didn't get the word. If the information is out there I could not find it. So back to my original question, is it safe to shoot .308 Win in rifles chambered for 7.62x51 (especially if it it headspaced per .308 requirements)? Also, anybody have CUP pressures for .308 Win?

[billamj]

Check Walt's sig, it might give you an idea of the person you are talking to. To answer your question, yes it is safe.