7.62 x 51 or .308

[HonkyTonkHale]

I have an M1A and have made a practice of shooting 7.62 x 51 ammo. I know that .308 ammo is very similar, but I have always assumed that 7.62 NATO would be more accurate and reliable. Will shooting .308 have a big impact, or less of an impact than switching between 147 gr and 168 gr ammo? Is the difference similar to the 5.56 vs .223 argument?

 

[CAR-AR-M16]

I have an M1A and have made a practice of shooting 7.62 x 51 ammo. I know that .308 ammo is very similar, but I have always assumed that 7.62 NATO would be more accurate and reliable. Will shooting .308 have a big impact, or less of an impact than switching between 147 gr and 168 gr ammo? Is the difference similar to the 5.56 vs .223 argument?

It is actually opposite. 5.56mm is loaded hotter than .223 Rem, 7.62mm is loaded weaker than .308 Win.

 

[HonkyTonkHale]

If it is the opposite of the 5.56 vs .223 scenario, does that mean that I should only shoot 7.62 NATO through an M1A, but it is safe to shoot 7.62 nato through a rifle chambered for .308?

 

[swampratt]

You can have some .308 ammo that produces less pressure than the 7.62 ammo and the opposite can be true.
Here is a lot of reading on the subject to twist your head a few times. some tests were performed by some of the posters..a good read.

http://m14forum.com/ammunition/100445-7-62-x-51-cartridge-vs-308-winchester-differences.html

 

[CAR-AR-M16]

Here is more info on the subject.

http://www.fulton-armory.com/%5Cfaqs%5CM14-FAQs%5C308.htm

 

[HonkyTonkHale]

Thanks everyone for your replies and reference material. It looks like I will need to do some studying before I think about shooting any .308 in my M1A.

 

[swampratt]

I would reload or at least measure your fired cases vs some fired cases from a .308 of the same ammo and go from there.
My reloads for my .308 are at the lower end of the loading scale and I would not be concerned with shooting them in any gun.
But it does not sound like you reload.

 

[Leggett71]

Have a Navy Garand in 7.62 x 51. Would never consider chambering a 308 round. All I have read in the Milsurps forums distinctly state not to use 308 in a garand chambered for 7.62. There is plenty of web articles noting the differences in dimensions between 308 and 7.62 also that the NATO stamped ammo is correct loads for the gas pressures required to operate the garand without an issue. You might also note there are some foreign NATO marked rounds that you need to avoid because they are still corrosive.

From my experience 7.62 chambered garand is a pleasure to shoot & very accurate.
Leggett

 

[Sanford]

FWIW, from the Springfield M1A manual:

The M1A is designed and built to specifications to shoot standard factory .308 made to SAAMI specifications or 7.62x51 NATO ammunition. The specifications for standard military ammunition include harder primers to withstand the slight indentation from the firing pin when the bolt chambers a cartridge. This slight indentation is normal. The use of civilian ammunition with more sensitive primers or handloads with commercial primers and/or improperly seated primers increase the risk of primer detonation when the bolt slams forward. This unexpected “slam fire” can occur even if the trigger is not being pulled and if the safety is on. Use of military specification ammunition will help avoid this. Every shooter should use extreme caution when loading this or any other firearm.

"CMP Special" .308 Garands are reportedly chambered to .308 standard commercial specs (Criterion barrel based on the old SA#11686514 barrel drawing number).

For whatever it's worth ... hope it helps.

 

[Cimarron]

For what it is worth you seem to be concerned with factory loaded ammunition. This is not a hard and fast rule but if you stay with 145g to 175g bullet weight ammunition you will probably be ok. The 168 and 175 are usually sold as match ammo. 145g-155g ammunition at around 2750 fps should ( I said should be ok). 168g ammo at around 2600-2650 fps should be ok as should 175g ammo at 2550-2600 fps. I shoot and reload a lot of M80 ammunition. It is true that some .308 Win. factory ammunition SHOULD NOT be used in the M1A/M14 platform. The heavier hunting loads should be avoided. Good luck.