M1A - 762x51 or .308... for the 18,451st time

[notalib]

I have heard several well informed and apperantly reliable sources on this forum and others that say do NOT use .308 in and M1A as they are spec'd for 7.62x51 and there is a 2K+ Max PSI diff between the 2.

I have called Springfield armory on 2 different ocasions and asked them what chambering the M1A has. Their response has been .308, and they say i can use either .308 or 7.62x51. I even mentioned that there is 7.62x51 stamped on the tang.

Is there someone out there that has reason to disputes this? Not trying to start WWIII.. just want to save a nice M1A frm going boom instead of bang.

 

[PatMcD]

.308 or 7.62; it doesn't make a difference.
What does make a difference is what weight bullet you use. Nothing over 168 unless you make some mods. Yes, you can use 175 target loads, but definitely no 180 grain hunting loads.

 

[Baystatesuks]

I am building a LR308 (which is neither here or there) but my understanding is both cartridges will headspace about the same in most rifles. I say about the same as rifles vary from barrel to barrel/bolt to bolt.

So check the headspace (or have a gunsmith do it) and that should tell you what is safe to use or not to use. In most instances both are safe from a headspace perspective but that is not always the case. You would ideally have both 7.62x51 and .308 GO, NO GO and FIELD gauges to check it out.

Heavy bullets tend to batter the older M1's. Try feeding it lower bullet weights such as 147 grain and see how it works. If you have excessive headspace and a hot loaded round, things may go bad.

 

[Sweeney]

Here's an explanation of the differences.

http://m14forum.com/gus-fisher/66601-little-bit-everything-do-headspace.html

 

[RKG]

More important than .308 vs. 7.62 is port pressure: if you are using factory loads, the box should be marked for use in M14/M1A. If handloads, no propellant slower than IMR4064.

 

[Swamp_Yankee]

I agree that .308 hunting ammo should be avoided. Aside from that, you should be fine. The worst case scenario is that eventually you bend the op rod. You would rather not but it's a $200 replacement part.

 

[Sir_Macadoo]

I shoot both (whatever i can find) in my HK91 clone. Never had an issue.

 

[soloman02]

wtf? No heavy loads (over 168gn) in an M1A? Can someone explain why? Kinda defeats the purpose of having a "Battle rifle" if it cannot shoot anything out there. Makes it kinda useless for when TSHTF cause you may not be able to find only 168 grain ammo.

 

[willbdavis]

Kinda defeats the purpose of having a "Battle rifle" if it cannot shoot anything out there.

Not really. The U.S. military doesn't spec the rifles to shoot whatever is found lying on the ground. Buy a bunch of milsurp 7.62 NATO ammo for go time.

 

[FPrice]

wtf? No heavy loads (over 168gn) in an M1A? Can someone explain why? Kinda defeats the purpose of having a "Battle rifle" if it cannot shoot anything out there. Makes it kinda useless for when TSHTF cause you may not be able to find only 168 grain ammo.

Probably because it wasn't designed as a "SHTF" firearm. More likely the idea(s) of a precision weapon and a supply chain that would keep your rifleman well-supplied with ammunition were in the minds of the logisticians than the scenarios we envision today.

 

[PatMcD]

wtf? No heavy loads (over 168gn) in an M1A? Can someone explain why? Kinda defeats the purpose of having a "Battle rifle" if it cannot shoot anything out there. Makes it kinda useless for when TSHTF cause you may not be able to find only 168 grain ammo.

The M14 (The Springfield M1A is the non-full-auto version) was designed around Nato ball ammo (147 FMJ). Like willbdavis said, it wasn't meant for soldiers to go down to the local hardware store to buy a box of ammo if they ran out.
It has to do with port pressure. The M14-system is a gas-operated piston, operating rod design. Too much of the wrong kind of pressure will batter the hell out of it. I'm not an expert on the technical points, but heavy loads meant for hunting (180's) use a slower powder that puts a lot of pressure for a long time on the system. Lighter bullets use faster powder that gets it out quick.
Personally, I've never seen or heard anybody actually damage an op-rod by doing this, and you know that out of the tens of thousands of M1A's that have been sold, somebody has to have put the "wrong" ammo in it. There is a company that sells a modified gas plug that supposedly allows use of heavy loads (Schuster, I think).

 

[Sweeney]

Go over the M14 Rifle Association board and ask a couple of the armorers there, specifically "T44E4" a friend of mine. He was an engineer at H&R building M1s and M14s. At his own business, Brookfield Precision Tool, he designed and built the first functional scope mounts for the M14, a design copied by Sadlak and SEI along with other M14 specific components. He also built the actual M25 sniper rifles the Secret Service used while guarding Bush Sr. up in Maine... and a spare or two )

 

[notalib]

Go over the M14 Rifle Association board and ask a couple of the armorers there, specifically "T44E4" a friend of mine. He was an engineer at H&R building M1s and M14s. At his own business, Brookfield Precision Tool, he designed and built the first functional scope mounts for the M14, a design copied by Sadlak and SEI along with other M14 specific components. He also built the actual M25 sniper rifles the Secret Service used while guarding Bush Sr. up in Maine... and a spare or two )

Tnx for the intor to an expert. I understand the diff in preasure between the 2 rounds, but if Springrield says their M1As are built for .308, then I should be safe to shoot anything.. 180s et al... I guess that was the crux of my question.

I'll ask the expert!!! I'll post any cool info I get back

 

[gunclinger]

There is also the issue of primer hardness. The M1A has a floating firing pin which supposedly means you need cartridges with harder (mil-spec) primers to avoid a slam-fire. Yes if you eject and examine a cartridge that has been just loaded into the M1A chamber by semi automatic action, you will see a light dimple in the primer. I have never heard a case of it happening, however.


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[terraformer]

.

 

[Sweeney]

There is also the issue of primer hardness. The M1A has a floating firing pin which supposedly means you need cartridges with harder (mil-spec) primers to avoid a slam-fire. Yes if you eject and examine a cartridge that has been just loaded into the M1A chamber by semi automatic action, you will see a light dimple in the primer. I have never heard a case of it happening, however.

This is only the case if the receiver 'safety bridge' is of incorrect geometry.

 

[CMEBoston]

The springfield M1A is chambered for .308( at least mine is) that means you can shoot .308 and 7.62mm. The (norinco, polytechs) variants are chambered in 7.62 and should not be used with .308 a .308 chamber is rated at a higher pressure than the 7.62.


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[calsdad]

Probably because it wasn't designed as a "SHTF" firearm. More likely the idea(s) of a precision weapon and a supply chain that would keep your rifleman well-supplied with ammunition were in the minds of the logisticians than the scenarios we envision today.

Yeah, exactly. I'm pretty sure the Army supply chain wasn't planning to have to be air dropping in pallet loads of 180 grain hunting loads to resupply you as your mowing down Russkies from your trench in the Fulda Gap.

It's a military rifle - it's uses military ammo.