Help. 7.62 Nato vs. .308 Win

[lgm270]

Question:  Is it safe to shoot commercial  308 in an Israeli mauser rebarreled for the 7.62 nato? 

I've read a bunch of on line stuff about the minor yet potentially significant differences between these two rounds and am still not sure what I can and  can't do.

Do I need to have the headspace checked first? 

[Mikey]

Igm:  #1 - it is always recommended to have the headspace on a mil-surp checked and would recommend you have that done.

#2:  The 7.62x51mm Nato cartridge and the 308 Winchester are dimensionally the same.  The Nato cartridge is a mil-spec round in the 47-50K psi range whereas the 308 is a commercial hunting version that often works at higher pressures in the 60K range.  Isreali Mausers are 7.72x51mm rifles based on the K98 Mauser action which is strong enough to handle the 308 sporting round but as always, have your headspace checked first.  HTH.  Mikey.

[Castaway]

Mikey, there is a slight difference in the drawings at the shoulder, but for practical purposes, the error in manufacturing of one will cross over to the dimensions of the other.  lgm270, heed Mikey's warning about pressure.

[Larry Gibson]

There is no difference in actual working pressures between the two. People miss read the figures and have come up with this myth.  As mentioned if the headspace is good then the rifle is fine with either type of ammunition.

Larry Gibson

[TrenchMud]

Are you referring to CUP vs. PSI  in how the pressure of the two are rated ?
I use the two interchangably just as I do the 5.56 and .223 Rem...

[Larry Gibson]

Are you referring to CUP vs. PSI  in how the pressure of the two are rated ?
I use the two interchangably just as I do the 5.56 and .223 Rem...

It is "apples vs oranges" when CUP and PSI are compared, a common error when some compare 7.62 to .308 and attempt to justify that they are really two different cartridges. Also you will hear claims that 7.62 NATO operates at 47,000 or as high as 52,000 psi and .308 Winchester operates at 62-65,000 psi. The military and SAMMI are the usual sources of these figures.  Granted the military specification sheets generally will provide a listed pressure, usually in psi's and generally in the 48-50,000 psi range. What does that "average pressure" really mean? It means there is usually a +/- of 7-8,000 psi to get that average pressure. Let's look at TM 9-1305-200, Small-Arms Ammunition, dated June 1961 and see what the specifications are for M80 Ball - the most common encountered 7.62 NATO ammunition. Quote; "Pressure; The average chamber pressure may vary from 45,000 psi to 65,000 psi, depending on the temperature."  Lets look at M59 Ball; Quote; "Pressure. The average pressure will not exceed 50,000 psi." Throw the +/- of 7-8,000 psi on top of those figures of the "average pressure" and the maximum allowable pressure jumps up to 72,000 psi for M80 Ball and 58,000 psi for M59 Ball. I will note here that M80 Ball was, in 1961, restricted to use in temperate climates. M80 Ball was, a couple years later, given the same specs as M59 Ball. Now then, let's look at what is quoted for the .308 Winchester; usually it is a SAMMI spec of something like the "maximum allowable" pressure is 58-60,000 psi. So if we look at what is the maximum allowable pressure for both the 7.62 NATO and the .308 Winchester we se they are the same for all intents and purposes. Keep in mind that most lots of military 7.62 or factory .308 Winchester do not normally operate at the maximums. The maximum allowable pressures are usually measured under extreme high temperatures (120-140s). 

Larry Gibson