Author Topic: Is the 7.62x51 ammo the same as 308 ammo?  (Read 22031 times)

Offline ncjeeper

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Is the 7.62x51 ammo the same as 308 ammo?
« on: May 21, 2011, 03:50:12 PM »
Just wondering. If so I was going to pick up some military surplus 7.62x51 to shoot in my 308 rifle.
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Offline Sister Wolf

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Re: Is the 7.62x51 ammo the same as 308 ammo?
« Reply #1 on: May 21, 2011, 03:56:30 PM »
No, they're not the same.

First, 7.62x51 Nato rounds are longer than 308 rounds. 
Second, 308 rounds are "hotter" than 7.62x51 rounds.

Thus, you can shoot 7.62x51 out of a 308 caliber rifle, but you can experience big problems if you try to shoot a 308 cartridge out of a rifle chambered for 7.62x51.

So the answer is yes, you can do what you are considering doing.  Just don't do it the other way around (buying 308 for a 7.62 chambered rifle). 

It's kinda like 223's and 5.56 rounds.  Sorta.


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Offline Pathfinder

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Re: Is the 7.62x51 ammo the same as 308 ammo?
« Reply #2 on: May 21, 2011, 04:38:58 PM »
SW, I think you have the .223/5.56x45 and .308/7.62x51 reversed. SAAMI specs for .308 and 7.62x51 NATO are generally considered identical. My reloading books are packed for the moment, so I can't quote chapter and verse at the moment. However, I checked the Hogdon site (http://data.hodgdon.com/cartridge_load.asp) and they do not even list anything for 7.62x51, but they do for the .308 Winchester.

However, what you said is absolutely true for the .223 and 5.56x45 - do NOT shoot a 5.56x45 NATO round in a .223; other way around is fine. The 5.56 spec allows ca. 10,000 more psi than the .223 IIRC.
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Goatdog62

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Re: Is the 7.62x51 ammo the same as 308 ammo?
« Reply #3 on: May 21, 2011, 08:13:59 PM »
As said, 7.62x51 in a .308 gun is okay. .308 ammo in a 7.62x51 is risky. Normally you'll be fine but a .308 bullet loaded to full industry standard fired out of a less-than-modern 7.62x51 could rupture. I would look for guns marked .308 if you were looking for a gun or ammo marked 7.62x51 NATO if you already have the gun.

Offline Sister Wolf

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Re: Is the 7.62x51 ammo the same as 308 ammo?
« Reply #4 on: May 21, 2011, 09:05:50 PM »
SW, I think you have the .223/5.56x45 and .308/7.62x51 reversed. SAAMI specs for .308 and 7.62x51 NATO are generally considered identical. My reloading books are packed for the moment, so I can't quote chapter and verse at the moment. However, I checked the Hogdon site (http://data.hodgdon.com/cartridge_load.asp) and they do not even list anything for 7.62x51, but they do for the .308 Winchester.

However, what you said is absolutely true for the .223 and 5.56x45 - do NOT shoot a 5.56x45 NATO round in a .223; other way around is fine. The 5.56 spec allows ca. 10,000 more psi than the .223 IIRC.

They are *almost* identical.  The 7.62x51 rounds are about a tenth of an inch longer than the 308 rounds (or thereabouts).  What Goaty said is exactly what I was trying to impart.  It could give you problems going the other way around.  It doesn't really matter, since he's got a 308, and wants to shoot 7.62x51 NATO rounds through it.  That's perfectly acceptable, regardless of the make/model of the 308.  :)


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SmartLikeTruck

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Re: Is the 7.62x51 ammo the same as 308 ammo?
« Reply #5 on: May 21, 2011, 11:24:27 PM »
Civilian market primers can also be too soft for military arms, right?

Offline hillclimber

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Re: Is the 7.62x51 ammo the same as 308 ammo?
« Reply #6 on: May 22, 2011, 08:09:34 AM »
Sort of...
Some civialian primers are soft enough to cause a "slam fire" in any semi auto that has a floating firing pin.
I've noticed that Federal primery are pretty soft. Had no problems withh CCI or Winchester.

The time you're most likley to get a slam fire is if you chamber a live round then let the bolt slam closed on it. If you let the bolt strip the live round from the chamber, you should be all set. ;)
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Offline Pathfinder

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Re: Is the 7.62x51 ammo the same as 308 ammo?
« Reply #7 on: May 22, 2011, 12:38:52 PM »
NCJeeper, the best advice I can give you is - Be careful of anything you read on "teh intertubes"! Try to find someone locally who reloads, preferably surplus brass, and ask them the question. Assuming s/he has all their fingers and never had a gun blow up on them, I would say you're good to go with their recommendations!  ;D

Goatie was right, if you have an antique or older, well used rifle, you do have to be extremely careful of what you shoot in it. Not so much because the steel might have failed (and if that is a worry, why are you shooting it at all?) but because use-wear may have done some weird things to tolerances, etc. making the rifle iffy to shoot anything but that which it was designed for - and maybe not even then. He's also right in that the .308 spec allows for slightly higher pressures, but nothing on the scale of the .223/5.56x45 pressure differences. That's why I said the .308 and 7.62x51 NATO rounds are "generally considered identical". Not precisely, but generally.

I found only a 1/100" difference in case length spec from the various reloading sites I checked, mostly based on the bullet being loaded - longer bullets require slightly shorter cases to meet the overall case length specification. Barnes had the shortest case length I found this morning - 2.005", whereas the spec seems to be more like 2.010 or 2.015" Also, Wikipedia (see my note above re' "teh intertubes"  ;) ) entries for both show no variation in case length for .308 and 7.62x51 NATO.

All that said, and cognizant of the fact I am saying this on "teh intertubes", bottom line? You should be good to go firing either round in a modern rifle of either marked caliber. Bullet weight will more likely have more bearing on your rifle's performance than case length, although the hard-core match people control everything from primer through case dimensions to powder and bullet. Enjoy.
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Offline Sister Wolf

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Re: Is the 7.62x51 ammo the same as 308 ammo?
« Reply #8 on: May 22, 2011, 01:03:12 PM »
For the record, I know absolutely nothing about reloading.  I just work in a gun shop, and am parroting what I've "learned" while working there.

If I'm wrong, I'm sorry.


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Offline ncjeeper

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Re: Is the 7.62x51 ammo the same as 308 ammo?
« Reply #9 on: May 22, 2011, 01:22:57 PM »
10-4, thanks.
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Offline hillclimber

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Re: Is the 7.62x51 ammo the same as 308 ammo?
« Reply #10 on: May 22, 2011, 02:19:03 PM »
Either way, surplus 7.62 is still safe to shoot in a modern 308. The other way around is when you should do your homework.

When I reload surplus brass I cut back on the powder by 10%. The surplus brass is quite a bit thicker than modern 308 brass.
You'd also want to think about what primers you use (magnum vs large rifle primers). There's quite a difference in power there.
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Offline Urban Knight

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Re: Is the 7.62x51 ammo the same as 308 ammo?
« Reply #11 on: March 11, 2012, 08:38:51 AM »
Gentlemen:

I reload .308 for use in a 7.62x51NATO select fire non surplus original battle rifle.  Should I be worried that I use .308 Winchester specs for use in my firearm?

Thank you for whatever info you may give.

Offline Truik

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Re: Is the 7.62x51 ammo the same as 308 ammo?
« Reply #12 on: March 11, 2012, 09:46:59 AM »
I was looking for 7.62x54 R the other day and someone tried to sell me 308

 ???

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Offline Sister Wolf

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Re: Is the 7.62x51 ammo the same as 308 ammo?
« Reply #13 on: March 11, 2012, 08:13:35 PM »
I was looking for 7.62x54 R the other day and someone tried to sell me 308

 ???

Wow. <shaking head>


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Offline hillclimber

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Re: Is the 7.62x51 ammo the same as 308 ammo?
« Reply #14 on: March 17, 2012, 10:04:36 AM »

Gentlemen:

I reload .308 for use in a 7.62x51NATO select fire non surplus original battle rifle.  Should I be worried that I use .308 Winchester specs for use in my firearm?

Thank you for whatever info you may give.
That depends....can you be more specific??
"Non-suplus,milspec, select fire" part has me scratching my head a little.
If you're talking about a modern weapon it may be chambered for 308 anyway.
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Offline hillclimber

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Re: Is the 7.62x51 ammo the same as 308 ammo?
« Reply #15 on: March 17, 2012, 10:05:45 AM »
For the record, I know absolutely nothing about reloading.  I just work in a gun shop, and am parroting what I've "learned" while working there.

If I'm wrong, I'm sorry.
You've been doing well so far ;)
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Offline KitsapRoadkill

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Re: Is the 7.62x51 ammo the same as 308 ammo?
« Reply #16 on: March 17, 2012, 06:48:21 PM »
I was looking for 7.62x54 R the other day and someone tried to sell me 308

That actually gives me a bit of a headache. Some people, man.

Either way, surplus 7.62 is still safe to shoot in a modern 308.

I've heard so many different opinions on what is considered a "modern" firearm that I've lost count. It ranges from the last two years all the way to the last fifty years to anything that uses a cartridge. Is there any definitive answer for what modern firearms are?
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Offline hillclimber

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Re: Is the 7.62x51 ammo the same as 308 ammo?
« Reply #17 on: March 19, 2012, 01:37:28 PM »
A "modern 308" will be marked "308win" on the barrel. Not with a vibrating pencil, but a manufacturer's chambering mark. Not trying to be a smarta$$ or anything... ;)
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Offline MilSpecIA

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Re: Is the 7.62x51 ammo the same as 308 ammo?
« Reply #18 on: March 20, 2012, 10:04:12 PM »
So far the answers to the original question;

Quote
Is the 7.62x51 ammo the same as 308 ammo? Just wondering. If so I was going to pick up some military surplus 7.62x51 to shoot in my 308 rifle.

Recognizing the actual intent of the question, the answer has been a solid "OK" to shoot 7.62x51 NATO through a .308. But when the thread turned to .308 through a 7.62x51 NATO (which seems is more common given the commercial availability of .308 ammunition) folks started getting all technical yet vague amid other off-topic questions. There was a lot of "ifs" but no solid explanation or answer. Then the question was asked again, but form a reloading angle;

Quote
I reload .308 for use in a 7.62x51NATO select fire non surplus original battle rifle.  Should I be worried that I use .308 Winchester specs for use in my firearm?

Assuming we define "battle rifle" as any popular 7.62 NATO platform produced since WWII, such as an M14, AR-10, or "other"; the question remains (1) can you safely fire, with no risk to self or firearm, industry standard .308 ammunition (such as Winchester or Remington) through a rifle chambered for 7.62x51 NATO, and (2) can you use those same industry specs when reloading .308 for a 7.62 NATO rifle again with no risk to self or weapon?

I'm very curious because both questions are relevant to myself (as I'm sure others) and when I called my firearm manufacturer they also were vague offering "industry premium" is preferred (but conveniently the most expensive), yet never came out and said .308 ammo is "OK" to fire through a 7.62x51 NATO rifle. My gun store sales rep just gave me a blank stare and after confessing no knowledge of reloading said, "yep" so I'm rather dubious there. Recognizing the difference in industry ammo, such as Winchester, and military surplus ammo, such as Lake City, is there any solid answer that can be provided from citable sources or is it all to remain personal opinion and Intertube hearsay? Personally, I'd like to know so I don't risk damage to my rifle that I bought just six months ago.

My kingdom for an answer!

Offline hillclimber

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Re: Is the 7.62x51 ammo the same as 308 ammo?
« Reply #19 on: March 21, 2012, 05:22:09 PM »
Well, if "cold hard fact" is what you want....it does depend on who you ask.
I can tell you this much, Springfield is vague about whether or not commercial 308win ammo is ok for use in their M1a rifles, or at least they were vague last I checked. I don't shoot it in mine very often, but during hunting season I have fired a few rounds of Winchester. In general, I myself do avoid using regular 308 because I handload, and have plenty of both match, and hunting ammo.
Now that being said, to the best of my knowledge, the biggest difference between 7.62x51mm and .308win is the thickness of the brass. The military brass is thicker, and will hold less powder. The same can be said for 556mm as opposed to 223rem. In both instances the military cases are (or may be) slightly longer at the neck, thus the commercial brass is shorter. I've found the length difference more often in 556 myself, but I've heard it said that it can be an issue with the 7.62 as well.
So, when I'm working my handloads, I just trim all the cases to the proper length for commercial specs. That takes care of any length problems, and leaves the capacity issues caused by the difference in brass thickness. To deal with that problem, I've reduced my personal powder charges by about 10%, and that has worked just fine for me for at least the last 10 years or so.
The thing is, with the commercial, store bought ammo, you just don't know what's in it. But, with the thinner brass, it will hold quite a bit more powder. I seriously doubt you'll ever have an issue with a M1a blowing up, because of using Win, Rem, etc, but A steady diet of it could cause premature wear issues.
It could be a little hard on your operating rod, locking lugs, roller, etc....

I really hopes this helps answer your question.
An M1a is what I'd consider a modern and durable weapon, and I'm sure it will hold up just fine.
I would worry more about some of the older mil-surp stuff, like the Indian SMLEs chambered for 7.62, and stuff like that.
Please bear in mind, I'm not a "gunsmith", but I've been doing this stuff for many years. So I guess it's better than advice from a internet mall ninja ;)
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Offline iam4liberty

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Re: Is the 7.62x51 ammo the same as 308 ammo?
« Reply #20 on: March 21, 2012, 09:00:32 PM »
The 308 Winchester and 7.62X51 NATO are indeed two separate chamberings and cartridges. Their specifications overlap so in many instances the cartridges can be interchanged in a given rifle. Almost all 7.62X51 NATO ammo is manufactured within .308W ammo specs and so are compatible with .308W chambered rifles.  However, the same is not true for .308W ammo with 7.62X51 NATO chambered rifles. This can lead to an unsafe situation in some rare instances.

Also, even if safe, some .308W ammo will not properly cycle semi-autos tuned for 7.62X51 due to different pressure distributions.  The max pressures actually aren't that different (most of the difference cited on internet blogs is due to how pressure is measured by military and civilian agencies).  But how that pressure unfolds at the extreme of the .308W specs can be problematic.  Also, the differences in brass thickness and the issues with reloading mentioned above are 100% correct. 

One of the best writeups I have seen on the topic was posted on surplusrifle.com several years ago.  Surplus collectors and reloaders are the ones most impacted by the differences and so generally have spent the most time on the topic.  The article doesn't take into account the variance in how pressures are calculated between the two so it may be overly cautious on that point.  But otherwise it provides very good information.  Unfortunately the articles from that great site seem to be down now.  But the articles are available on archive.org's "way back machine".  See below for further details on this topic:

http://web.archive.org/web/20061113053724/http://www.surplusrifle.com/shooting2006/308vs762nato/index.asp
http://web.archive.org/web/20061113071848/http://www.surplusrifle.com/shooting2006/update308vs762nato/index.asp

The wayback machine was running a little slow so it may take a while to come up.

Offline MilSpecIA

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Re: Is the 7.62x51 ammo the same as 308 ammo?
« Reply #21 on: March 24, 2012, 08:21:40 PM »
Really what we have is a multi-way discussion. After doing a lot of research, phone calls, and discussion with my local gunsmith there's several ways to approach this;

For the "buy-and-shoot" consumer .308 and 7.62x51 NATO are largely interchangeable at the commercial level (meaning you're buying Remington, Winchester, etc). Care has to be exercised however as less-than-modern rifles, non-US produced rifles, or antiques  chambered for 7.62x51 NATO may not be able to safely cycle and fire modern commercial ammo with their varying loads and differences in manufacturing. Also, commercial ammo comes in varying types, such as ball, FMJ, BT, etc. with differences in pressure and velocity. As commercially produced 7.62x51 NATO is within .308 tolerances it can be shot out of a .308 with no problems. However, the powder charge in commercial .308 is slightly more than 7.62x51 NATO thus the pressures are slightly higher (although some manufactures, such as Federal offer low-pressure .308 ammo or vary the grain of the bullet). Over a lengthly period of time, or high-volume of fire, this higher pressure can prematurely wear on the components of the rifle, starting within the chamber, bolt, and rifling first. So the answer I got from my rifle manufacturer, research, and local smith is; yes, you can shoot 7.62x51 NATO out of a .308 rifle. And you can also shoot .308 out of a modern 7.62x51 NATO rifle, but exercise caution and know what kind of ammo your using and the age of your weapon.

Now reloading gets a little more intense.

When reloading Mil-Surp 7.62x51 NATO ammo, it has a thicker cartridge and longer neck than commercial .308/7.62x51 NATO ammo. Thus when reloading Mil-Surp ammo to commercial specs you will need to check the length of the cartridge and possibly trim it down (some Mil-Surp ammo is produced by non-US countries, or oppositely is produced in the US and intended for countries elsewhere thus the cartridge may have minor differences in length). Also when using commercial specs reduce the amount of the powder charge going into the Mil-Surp ammo by 10% (this accounts for the differences in volume between Mil-Surp ammo and commercial .308/7.62x51 NATO ammo as commercial ammo has a thinner cartridge and thus holds more powder). If you're reloading commercial .308/7.62x51 NATO ammo the constant advice I received is have several reloading books and cross-reference the measurements for .308/7.62x51 NATO. You can also "tweak" your own recipe to get more/less pressure but that's on your own preference.

I think that covers all the bases, but as always if anyone else has something to further or discuss I'm always open to hear it.

Offline nelson96

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Re: Is the 7.62x51 ammo the same as 308 ammo?
« Reply #22 on: March 24, 2012, 09:13:35 PM »
Like you need another comment on the subject  :o  but I've always been told you are pretty safe on the most part, if you use these few rules . . . 
  • Bolt action rifles primarily use "full length" sized cartridges.  This is what you are commonly going to find with .308 ammo (commercial and military)
  • Semi-auto rifles primarily use "small base" sized cartridges.  This is what you are commonly going to find in 7.62x51 ammo.
  • Know your pressures.  Military brass is thicker thus will have higher pressures if loading with the same grains of powder as one would use for commercial brass (which is thinner).
  • When determining grains of powder to use, start light and work your load up as needed for accuracy.  High pressure signatures could include all or one of the following . . .  flattened primers, expanded case heads and ejector marks.
These rules don't "always" apply (ie.  my brother uses full length'd ammo in his AR-10 all the time)
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Offline hillclimber

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Re: Is the 7.62x51 ammo the same as 308 ammo?
« Reply #23 on: March 25, 2012, 07:54:22 AM »
MilSpec, If you knew all this stuff to start with, why all the frustration over an answer that you obviously already knew to start with??
Was this a test??
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Offline Sister Wolf

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Re: Is the 7.62x51 ammo the same as 308 ammo?
« Reply #24 on: March 25, 2012, 12:43:52 PM »
MilSpec, If you knew all this stuff to start with, why all the frustration over an answer that you obviously already knew to start with??
Was this a test??

I don't think he knew until yesterday, bro. I didn't get the impression that "after doing a lot of research, phone calls, and discussion with my local gunsmith" was a lie. Nor did I get the impression that "my kingdom for an answer!" was a lie.


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Offline hillclimber

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Re: Is the 7.62x51 ammo the same as 308 ammo?
« Reply #25 on: March 25, 2012, 02:05:53 PM »
Was just curious if I might have a "new kingdom" in my future. ;)

Can barely pay the taxes on the one I have now...LOL
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Offline joeinwv

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Re: Is the 7.62x51 ammo the same as 308 ammo?
« Reply #26 on: March 25, 2012, 04:42:49 PM »
W...
Now that being said, to the best of my knowledge, the biggest difference between 7.62x51mm and .308win is the thickness of the brass. The military brass is thicker, and will hold less powder. The same can be said for 556mm as opposed to 223rem. In both instances the military cases are (or may be) slightly longer at the neck, thus the commercial brass is shorter. .....But, with the thinner brass, it will hold quite a bit more powder. I seriously doubt you'll ever have an issue with a M1a blowing up, because of using Win, Rem, etc, but A steady diet of it could cause premature wear issues.
It could be a little hard on your operating rod, locking lugs, roller, etc....

I really hopes this helps answer your question.
An M1a is what I'd consider a modern and durable weapon, and I'm sure it will hold up just fine.
I would worry more about some of the older mil-surp stuff, like the Indian SMLEs chambered for 7.62, and stuff like that.
Please bear in mind, I'm not a "gunsmith", but I've been doing this stuff for many years. So I guess it's better than advice from a internet mall ninja ;)

I agree with all of this..

Offline MilSpecIA

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Re: Is the 7.62x51 ammo the same as 308 ammo?
« Reply #27 on: March 25, 2012, 10:12:28 PM »
Quote
MilSpec, If you knew all this stuff to start with, why all the frustration over an answer that you obviously already knew to start with?? Was this a test??

No, I am leading into reloading and have been shooting .308 for a while and really wanted to do some research (shy of calling Federal itself, but I didn't want to wade through a ton of BS to get to talk to someone there who "might" know) for an answer. But what is a community if that knowledge isn't shared? So I figured I'd share it with you all. Didn't think you'd dig all the statistical data but just the short and sweet of it all.

Offline hillclimber

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Re: Is the 7.62x51 ammo the same as 308 ammo?
« Reply #28 on: March 26, 2012, 01:29:47 PM »
No sweat, and like I said before, I hope the info was a help.

When handloading, be careful with rifles that have a floating firing pin. Most US military rifles have floating firing pins, meaning the pin itself is not under spring pressure.
Federal primers are a little softer than some of the others and could cause you trouble.
You can buy "mil-spec" primers, but I usually just use CCI or Winchester primers for my semi auto stuff.
 
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Offline nelson96

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Re: Is the 7.62x51 ammo the same as 308 ammo?
« Reply #29 on: March 26, 2012, 01:56:18 PM »
You can buy "mil-spec" primers, but I usually just use CCI or Winchester primers for my semi auto stuff.

Me too . . . .  I don't use mil-spec, I only use CCI primers, and I only use Winchester brass. . . . .  Fort bolt guns and semi-auto.
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