in a 308 rifle can you fire 7.62x51?

[CaliB&R]

My FAL is chambered for 7.62x51mm, and I've shot PMC and Winchester .308 with no issues. Usually run the German DAG 7.62 through it only cause its the cheapest in my area. Not sure if the DAG is surplus or new, but it runs reliably.

[hammerhands32]

looks like all dsa fal's are chambered in .308?

http://www.dsarms.com/FAL-SA58%20Rifles/products/8/

Sorrry for the fal thread jack

[captbilly]

Thanks for the great explanation.

The basic rule of thumb is that a .308 rifle can handle 7.62x51 ammo. But it's not about pressure, per se.

The SAMMI .308 specs are in Piezo-measured PSI. Military specs are derived from crusher-measured CUP (Copper Units of Pressure). The two scales can be loosely correlated using the formula 1.5 x CUP - 18,000 = PSI. (NOTE: there is NO direct correlation between the two systems! This formula is good for "rule of thumb" only.)

Using this formula the measured pressures in a 7.62x51 round in SAMMI PSI is 1.5 x 52,000 - 18,000 = 60,000. So the maximum chamber pressures for both rounds are not as far apart as they appear on paper.

Headspace should also be watched as putting a long 7.62x51 round in a tightly chambered .308 may result in bullet set back. That can raise chamber pressures significantly. Also, the slow burning powders used in some modern .308 rounds increase port pressures which can play havoc on auto loading military rifles.

As an example, my M14 and M1A are chambered for 7.62x51. They can also be fed certain commercial .308 WIN rounds because they are headspaced tightly enough AND because those rounds are made with a slow burning powder.

As an aside, with auto loaders there is also the consideration of using harder primers to avoid slam fires.

So, are the .308 and 7.62x51 interchangeable? Well, it depends.

(I realize a lot of this is a repeat of the discussion linked above. But I spent a lot of time typing it and didn't want to waste all these letters.)

I was aware that Sammi and NATO used different measuring systems but I did not know what the actual differences were. You often see articles and posts where people are alarmed by the substantial apparent difference in pressure spec for 7.62 vs. .308 or for 5.56 vs. .223, but as you say these are not comparable numbers. In reality the allowable pressure in the NATO and Sammi equivalent cartridges are very nearly the same, it is only the equipment used for the measurements that account for the large difference in specification. We see this sort of thing in engineering and physics all the time, where measurements with different equipment can give hugely different numbers for the same actual physical phenomenon.

[terry4130]

What about in a bolt gun like a rem 700

[EvolvedRaven]

What about in a bolt gun like a rem 700

I was wondering this too, but did a google search and it is ok to shoot a 7.62 round from your Remington 700 in .308...

[NoExpert]

It's all about head space...

1.628" to 1.630" I'd only shoot commercial .308

1.631" to 1.634" I would shoot both .308 and 7.62X51

1.635 and up to NATO max I'd only shoot 7.62X51

I had my rifle's head space set at 1.632" and shoot both with no problems. I got these numbers from Helmut over at Krieger when I was having my barrel head spaced.

[MudCamper]

It's all about head space...

1.628" to 1.630" I'd only shoot commercial .308

1.631" to 1.634" I would shoot both .308 and 7.62X51

1.635 and up to NATO max I'd only shoot 7.62X51

I had my rifle's head space set at 1.632" and shoot both with no problems. I got these numbers from Helmut over at Krieger when I was having my barrel head spaced.

This is key. You actually had your chamber machined for it. Most guns will need this, but most intarweb experts don't tell you this. Let me quote from the article I linked:

don't think for a second that you won't hear from otherwise educated people that there is no difference between the two cartridges. I doubt the truth will become popular in this century. Just remember that there is a difference & that as long as you're aware of the specifics of your rifle you can decide for yourself if you can interchange the two cartridges. Most important is that whether you can or can't interchange them you'll understand why

[NoExpert]

This is key. You actually had your chamber machined for it. Most guns will need this, but most intarweb experts don't tell you this.

Yeah, most just say "Mine shoots both fine." Well, yours might but the next guy's might not depending on his chamber. This is especially true with gas guns vs. bolt guns. Bolt guns are more precise and usually on the tight side of the specs, so if they say .308, they usually mean it. Gas guns are a little more forgiving since it's expected to get carbon in the chamber (nature of the beast) so they're usually in the mid range of the specs.

Regardless, if you want to shoot both, the only way to do so safely is to have your head space checked... Use Clymer gauges if you can, they tend to be more accurate. If it's on the tight side and you have a non lined barrel you can have the head space reamed to work with both. If it's too loose, sorry, you're stuck with 7.62X51.