.308 in a 7.62x51

[crbutler]

Farmerj, you are not talking the same thing. You seem to be confusing the ammo with the chamber.

SAAMI states that the cartridges are interchangeable dimensionally (ie exterior dimensions).

Yes there is a small difference in the rifle's chamber...but the AMMO is the same, except that the military stuff is a bit higher pressure and has a smaller internal volume case- read thicker brass- that was intended to prevent problems with machine gun fire (cook off, dirty gas systems, etc.)

Most of the chamber spec sheets I have seen do indicate the .308 CHAMBER is shorter, but they also note 0.015" is the allowable variance- thus a .308 on the long side is larger than a 7.62x51 on the short side for a chamber. Remember that a no go gauge is a oversize gauge to call cut off of max acceptable headspace.

The 7.62 is a bit bigger chamber wise- it is intended to be a bit looser so as to deal with dirt, build up, etc. for military weapons in combat. That is why match rifles are specifically cut to minimum chamber dimensions and why service arms are usually not as accurate as match guns.

The ammo is for all senses and purposes identical. (yes if you were using a weak action with NATO spec you could damage your rifle with repeated firings, but...)

While if you had a long chambered 7.62, and you always reloaded to spec length, your brass life would be shortened, it still would not be unsafe as factory ammo, nor would it be as reloads if you made sure of the integrity of the case each time you reloaded. You just have to make sure you check the brass is not getting thin in the web each time you reload it, which you should be doing anyhow with all your brass.

If you don't want to use NATO spec in a .308 chamber, you are certainly not being forced to; but then again, you are not knowing what you are speaking of if you just plain declare it "unsafe."

And the thousands of high power shooters using tight chambered .308 win guns with lake city surplus brass are not an accident waiting to happen...

[OldmanFCSA]

Dimensionally the same?

Wow.........



That's as far from the truth as you can get.

And being on the phone, not on my computer, I don't care to pull the facts together for that ********.
http://www.fulton-armory.com/%5Cfaqs%5C ... %5C308.htm
Sam is right for wanting to eat him up on this topic. Along with a bunch of others.


I'm outta here now. It's going down hill and I don't care to participate any more.

Cartridge case dimensions are identical. Chamber dimensions have the potential to be oversize on all semi-auto 7.62X51 platforms to allow for military firing conditions, which don't apply to most 308WIN hunting rifles.

Pressures are different because SAAMI measures pressure at the case head and NATO specification call for reading pressures at case mouths. This is due to the 7.62X51 typically being a semi-auto firearm whose gas pressure must be carefully regulated to promote best reliability. I have read that 7.52X51 is 50,000 PSI and 308WIN is 62,000 PSI = but again, where pressure is measured is the main difference between the two cartridges.

"Sam is right for wanting to eat him up on this topic. Along with a bunch of others.
I'm outta here now. It's going down hill and I don't care to participate any more."

This approach will surely destroy MN Gun Talk as the go-to Gun Forum in MN - let's all become sarcastic S-O-B's eating up noobies, spitting them out, how dare they come to OUR FORUM and ask questions about how to proceed properly.

[Seismic Sam]

Actually, all I said was that I was going out for supplies. No criticism one way or the other on the actual subject. Everybody who knew something chimed in, but I couldn't resist the temptation to post that. It's been soooo long since I had a juicy n00b sammich that I can wipe the tears out of my eyes with the slack in my belly...... Waaaaaahhhhh!!!!

[OldmanFCSA]

Thank you Sam.

Unfortunately, our reputations precede us in our actions.

[igofast]

Here is an infographic. I have seen (on the internet - so grain of salt) compelling data that you could interchange the 2, but I wouldn't. Rule of thumb: .223 is ok in 5.56, 7.62 is ok in .308 - the other ways around are not necessarily ok.

[xd ED]

Regarding the above graphic:

it states: ".308 WIN is designed to withstand 24% more pressure than 7.62 x 51mm."

as well as

“Military Surplus 7.62 x 51mm brass cases are thicker than commercially manufactured .308 WIN brass cases….”

To me this seems contradictory;
The thicker brass:
(a) should, I believe withstand greater pressure
and
(b) -given thicker case material, and the same outside dimensions, makes for a smaller interior volume, and thus a higher pressure; other things being equal.
What am I missing?

Thanks

[OldmanFCSA]

Nothing.

308WIN can withstand more pressure BECAUSE it will be used in a very tight chamber which prevents over-stressing the brass casing.

7.62X51 can withstand its pressure operating range because it has the thicker walls and is designed as to never be re-used for military purposes again, thus case expansion and case-head set-back during firing is a non-issue as long as new rounds do not fail in the chamber of military rifles.

I have a slight dis-agreement with the picture defining specified chamber length, but will let it go for now. I need to do more reading.

SO BASED ON WHAT HAS BEEN PRESENTED:

I will change my position - DO NOT use 308WIN in 7.62X51 chambers IF you have not verified chamber specifications.
Due to the possibility of the military 7.62X51 chamber being drastically oversize as compared to a standard 308WIN chamber, the thinner brass casing of the 308WIN may rupture in extreme situations. It would be considered scrap afterwards due to extreme stretching of brass casing in areas than cannot be re-sized back to original specifications.

Due to MY rifles being checked out with chamber gauges and being within 0.003" variation, I will continue with MY PRACTICES.

[xd ED]

Thanks Doug

ETA:
Looking at the website for the Mossberg MVP Series of rifles, they have 2 caliber choices.

The are listed as "5.56mmNATO (.223 REM.)", and "7.62mm NATO (.308 WIN)".

Interesting that a barrel would have been stamped for only the 7.62 round.

[UnaStamus]

I would be surprised if the Mossberg was actually 7.62x51 spec. They made a run of "5.56" barrels for S&W M&P15 rifles, and all were actually .223Rem spec and NOT 5.56, despite being marked as 5.56 NATO. This caused a lot of issues with vertical stringing and so forth, and it caused a recall. Mossberg didn't know the difference.

I would also question why you would buy a Mossberg over an alternative rifle like a Savage, Tikka or Remington, all of which would be much more accurate and reliable, but I guess we're past that point in the discussion.

[Squib Joe]

I would be surprised if the Mossberg was actually 7.62x51 spec. They made a run of "5.56" barrels for S&W M&P15 rifles, and all were actually .223Rem spec and NOT 5.56, despite being marked as 5.56 NATO. This caused a lot of issues with vertical stringing and so forth, and it caused a recall. Mossberg didn't know the difference.

I would also question why you would buy a Mossberg over an alternative rifle like a Savage, Tikka or Remington, all of which would be much more accurate and reliable, but I guess we're past that point in the discussion.

Mossberg has stated that they very deliberately used a 7.62x51 barrel in the MVP rifles so that a wider range of ammo can be used, in particular both 308 and 7.62 NATO. They said it, not me.

This isn't a bad rifle. I like the idea that you can use DPMS, Magpul, even M14 pattern mags in it

[20mm]

If you get a good deal on .270 you can also use that. Just don't reload it.

[goosed]

If you get a good deal on .270 you can also use that. Just don't reload it.

Are you suggesting the use of .270win ammo in a 7.62x51 Chamber?

[20mm]

If you get a good deal on .270 you can also use that. Just don't reload it.

Are you suggesting the use of .270win ammo in a 7.62x51 Chamber?

Yes, but it takes more skill to get accurate shots because you have to take into account a number of varying ballistic factors.

[OldmanFCSA]

If you get a good deal on .270 you can also use that. Just don't reload it.

Are you suggesting the use of .270win ammo in a 7.62x51 Chamber?

Yes, but it takes more skill to get accurate shots because you have to take into account a number of varying ballistic factors.

\


This one definitely needs a well thought out response by the 800 pound gorilla, especially a very hungry gorilla.

[Erud]

If you get a good deal on .270 you can also use that. Just don't reload it.

Are you suggesting the use of .270win ammo in a 7.62x51 Chamber?

Yes, but it takes more skill to get accurate shots because you have to take into account a number of varying ballistic factors.

Yeah, like the bullet only contacting 1 land of the rifling at a time...

More gems of wisdom from 20mm.