GUN 7.62x51 and .308, can they be interchanged

i was just separating some brass i got from the range a while back, and it turns out i have 21 7.62x51 casings, and 2 .308 casings. ive read some people saying you can use them and some people saying you cant.

im thinking of getting the a .308 remington 700 somtime in '09 and it would be sweet if i could use these casings

 

I use the 7.62 NATO cases when I reload most of the time. It shouldn't be a problem from a feeding standpoint, but the brass on the NATO cases is usually thicker, so using NATO and .308 brass in the same group of cartridges could affect the accuracy overall. I load my target loads in NATO cases and my hunting loads in commercial brass. I don't do this for any other reason than I have a ton of Winchester NATO brass, and not much commercial Federal stuff, and I go through many more target loads than I do hunting ones. The other unsubstantiated reason I do this is because the thicker brass could hold up better to more reloading.

 

if i remember correctly, i can probably get about 3 reloads out of my rifle brass?

 

It depends how you size them. If you have a bolt or single-shot and just neck-size, you should be able to get many more than that if you are not loading insanely hot loads. If you are using a semi or just choose to full length size you should get more than 3, but not as many as just neck-sized brass. I've heard of guys with custom calibers reloading brass dozens of times by neck sizing only. At any rate, brass should be checked before reloading for potential problems. Also, different brass will give you different results. S&B 7.62x54R brass will hardly stand getting reloaded once, but some of my military 7.62 NATO brass has been reloaded 4-5 times with no problems yet.

 

military brass is thicker and thus has a smaller combustion area which will cause higher pressures; you'll want to start at minimum listed loads or even a couple of grains lower to be safe.

 

I shoot both out of my M1A and have never had an issue

 

now, what would happen if a round cracked while in the chamber.

im sure we all have seen this video, but im not exactly sure what happened [sorry i dont know how to embed]

http://www.youtube.com/watch?v=Oh1lyMyejpI

 

The Springfield M1A is designed for shooting the higher pressure .308 Winchester cartridge. Older Mausers and other actions that were converted 40 years ago were proofed for the 7.62x51 loading. IIRC the .308 Win has about 5,000 PSI more maximum allowed chamber pressure than the 7.62x51 and the 8x57 cartridge that most converted rifles used before they were rechambered.

 

so its safe to say that if i get a rem700 in .308 it would be able to handle the pressure of the 7.62 cuz it is in a fact lower presser.

 

While pressure is the popular theory on old rifles and .308, I believe it is incorrect. Both rounds will chuck the same weight projectile at the same speed, I don't think we're seeing much of a pressure difference. The confusion comes from the two different systems each uses to measure chamber pressure. The real problem, I believe, is chamber length.

Lets look at the numbers for chamber gauges for the two calibers:
.308 GO 1.630"
.308 NO-GO 1.634"
.308 FIELD 1.638"
7.62 GO 1.6355"
7.62 NO-GO 1.6405"
7.62 FIELD 1.6455"

Among the several differences there, notice that the nato field gauge is significantly longer than the .308 gauge? I would personally put a .308 field gauge into any milsurp I wanted to shoot .308 through. If it closed on a .308 field gauge, I wouldn't shoot .308 through it. I would then check to be sure it was even safe to fire nato in it.

A gun like a 700 has its chamber cut for the .308 lengths so it shouldn't be an issue with either. Military guns chambered for nato, I'd test.

 

Absolutely. I've shot 7.62x51 out of my .308 rifles for years and I know others do too.

 

So I guess the consensus is that I shouldn't shoot .308 out of my CETME.