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Question about 308/7.62 Nato

Discussion in 'Ammunition & Reloading' started by SDR, Dec 21, 2008.

  1. SDR

    SDR Clackamas County, Oregon Silver Vendor Silver Vendor

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    I'm just getting into the semi auto's...
    I have been told that 5.56 should not be mixed with .223...
    Steel cased should not be used in a gun that was not built for it...

    My question is is it the same for 308 verses 7.62Nato....
    Will brass 7.62Nato work with no side affects in a 308...
    I will appreciate any and all Imfo
     
  2. PhysicsGuy

    PhysicsGuy Corvallis, OR Resident Science Nut

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    What you hear is not always the truth;

    There are significant differences between 5.56 and .223, and between .308 and 7.62x51. As far as functionality/reliability/safety, it is a good idea not to use 5.56 in a .223 gun, but most .223 milspec ARs have 5.56 chambers, so you are safe with both.

    As far as .308 vs 7.62, from what I know it should be safe to use either in the other ones chamber, since there aren't pressure/external dimension differences. (correct me if I am wrong)

    If you are wondering, the nato brass is built to withstand pressures higher than commercial ammunition.

    As far as using steel cases, people will argue both ways. Either way I don't see any problem running it in any firearms, except for it is very dirty and inconsistent.
     
  3. OFADAN

    OFADAN Brownsville, OR Well-Known Member

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    RE: Steel cases

    I admit I'm still a novice at all this and a student...so please understand all I can contribute is what little I learned in gunsmithing school, attending numerious factory armorer courses, and from my contacts in the firearms manufacturing. The message I've gotten very clearly from these sources is steel case ammo in SAAMI spec'd rifles and handguns which are designed for softer "brass" cases can have a negative effect. The most notable is the extractor. Steel cases are extremely hard on rifles/handguns extractors.

    The exception to this is any firearm designed for steel cases such as the SKS, AK, or AKM for example. The only SAAMI spec'd rifle I'm aware of that is specifically designed with a bullet proof extractor is the Robinson XCR. Alex Robinson is or has redesigned his XCR so it could take advantage of steel cases as he is convinced the day will come when that is the only ammo we can obtain.

    I realize this is a rifle related thread...but this is an email I recieved from John Farnam a while back about the issues they're having (which parallels with the issues we have at OFA) using steel cased ammo in SAAMI guns.

    --------------------

    We just finished a three-day Police Pistol Course. Each student fired 2,500 rounds. Two officers showed up with Wolf 40S&W ammunition. Their department didn't want to 'spend a lot of money on ammunition!'

    It was brutal and painful to watch their guns break, right before our eyes. First, came numerous, minor malfunctions. Then came the serious malfunctions. Finally, their pistols just broke. The first was a Beretta 92F. At 1000 rounds, the extractor claw sheared right off. At 2000 rounds, the Glock finally broke its extractor too. The good news was that we had Glock Armorer there, and the Glock was back up and running within a few minutes. The Beretta shooter, unfortunately, had a long, round-trip home, on day two, in order to retrieve a replacement pistol.
     
  4. wichaka

    wichaka Wa State Well-Known Member

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    Steel on steel is never a good thing without lube, and you can't lube your ammo...so...

    Have heard many stories about having no problems with steel cased ammo, but have seen the long term effects of it...not a good thing, and can be spendy to fix.
     
  5. Dutchy556

    Dutchy556 Bend, OR Member

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    In regards to 7.62 vs. .308 it is my understanding that the SAAMI spec .308 can in fact have higher chamber pressure than nato spec 7.62. This, combined with a thinner case wall means .308 can potentially give you problems in a NATO spec chamber, whereas 7.62 in a .308 would be good to go.

    Kind of the opposite situation of .223/5.56


    Anyone else want to back me up on this (or tell me I'm wrong)?

    linkage that agrees with this position:

    http://www.thegunzone.com/30cal.html


    http://www.ar15.com/forums/topic.html?b=1&f=5&t=794421

    http://www.surplusrifle.com/shooting2006/308vs762nato/index.asp
     
    Last edited: Dec 21, 2008
  6. SDR

    SDR Clackamas County, Oregon Silver Vendor Silver Vendor

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    Lots of Information....
    Thank You!
     
  7. RVTECH

    RVTECH LaPine Well-Known Member

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    Did not see it mentioned but I read somewhere, some time ago, the lacquer coating on steel cased ammo can melt and flake off in high heat situations causing problems. I cannot cite any personal personal experience with steel cased ammo other than a few mags of it ran through an AK I once owned and a freebee 1/2 box of 45 ACP I ran through my 1911 A1. I did notice the .45 did not feed as well with the steel cased ammo though.
     
  8. Dutchy556

    Dutchy556 Bend, OR Member

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    AFAIK, it is a myth that the industrial lacquer used on steel casings actually "melts" to your chamber. Take a blowtorch to a casing (AN EMPTY ONE) and see for yourself what it takes to get the lacquer viscous...

    What is happening is the steel cases don't expand like brass, and they leave just enough room for a bunch of fouling to come back into the chamber and eventually start causing stuck cases (especially if you switch to brass after steel).

    In any case, all the new steel cased stuff is polymer coated so even if you do think the lacquer melts that's a not an issue any more. The fouling issue is still a problem though. I have shot plenty of steel cased stuff (Wolf, Silver Bear) out of my ARs and the only problems I've had are stuck casing like I described -when you get them out there's caked on carbon fouling on them so it's pretty obvious what the problem is to me.


    All of that said, there may be SOME older lacquered ammo out there with lacquer that causes fouling. I have a friend whose into C&R and according to him some of his old russian guns have lacquer built up in the chambers... whether this is lacquer of fouling similar to what I described earlier I don't know...

    In any case, steel is dirty, steel might stick sometimes, steel can wear your extractor a bit, etc etc. Lots of people use it as range ammo all the time an have no problems. Others say that it is the worst stuff ever. I don't use it often but I'll shoot it if that's whats sitting around. YMMV
     
    Last edited: Dec 23, 2008
  9. SDR

    SDR Clackamas County, Oregon Silver Vendor Silver Vendor

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    Thank You,
    All information is much appreciated.
    I see a few opinions on this subject,With all this information I have formed my own.
    Thanks Again
     
  10. Dutchy556

    Dutchy556 Bend, OR Member

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    That's the way to do it (form one's own opinion...)! :thumbup:
     
  11. OFADAN

    OFADAN Brownsville, OR Well-Known Member

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    Yep...we're just like Fox News..."we report you decide!"
     
  12. PhysicsGuy

    PhysicsGuy Corvallis, OR Resident Science Nut

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    Here is some additional information regarding 7.62/.308, and .223/5.56

    "....resulted in a lengthening of the throat in the 5.56 mm chamber. Thus, while .223 Remington ammunition can be safely fired in a 5.56 mm chambered gun, firing 5.56 mm ammunition in a .223 Remington chamber may produce pressures in excess of even the 5.56 mm specifications due to the shorter throat." - wiki

    Also .308 cartridge data shows that it is rated to 62,000 psi, and 7.62x51 is rated to 60,200 psi.

    Also a good reference for "unsafe" combination (listed by SAAMI), can be found here; http://www.saami.org/Unsafe_Combinations.cfm

    Note that it lists 5.56 as unsafe to fire in a .223
     
  13. Dutchy556

    Dutchy556 Bend, OR Member

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    Great link PhysicsGuy...

    Yeah 5.56 in .223 not a good plan...


    Now I have to go figure out the pressure diff. between 9mm para and 9mm NATO... something new to learn every day...

    Am I the only one who thinks that it would be cool to get together a tacked thread with this sort of info in it - what to not chamber in what and why (dimensions, pressure, etc) linked to good resources?
     
  14. PhysicsGuy

    PhysicsGuy Corvallis, OR Resident Science Nut

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    Yeah I too noticed the 9mm nato reference on the SAAMI site, I do not know what the exact pressure difference is, but I am sure it is listed because there are several different loads for 9mm IIRC, so some of these exceed saami pressures, but also I have never seen 9mm nato ammo for sale.

    This is a really good idea, feel free to start a thread if you want, and I'm sure joey can sticky it for you.


    oh and thanks Dutchy
     
  15. Tecla

    Tecla Portland New Member

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    I did some pretty extensive research on the .308 vs 7.62 issue. What I came to was that if you have an old and worn 7.62 chamber there is a possibility that .308 could run into problems. The 7.62 chamber can potentially be longer than the field reject length of .308. So if you're getting a gun from an unknown source checking the headspace is a good idea.

    Many people say there are possible chamber pressure issues and site 62000 vs 50000 numbers. These two are measured using different methods and you can't really compare them, 50k CUP vs 62k transducer.

    See here for more info.

    http://www.thegunzone.com/30cal.html

    That being said, I put 40 rounds of Walmart .308 Federal Power-shok through my FAL on Saturday without any trouble.

    Also SAAMI does not list them as an unsafe combination. I have read that if you fire .308 in a 7.62 chamber and then reload it, it may not fit well in a .308 chamber due to being expanded or flowing or whatever to fill the 7.62 chamber.
     
  16. Hotwheelz

    Hotwheelz Pierce County Member

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    Thanks for that info I never thought of that or heard explained that way I do believe this may have been my problem years ago in my 45 , I really thought it was the laqure....