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7.62

Discussion in 'Mossberg MVP Bolt Action' started by Jeremyjms06, Dec 7, 2015.

  1. Jeremyjms06

    Jeremyjms06 Copper BB

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    So I know you're not suppose to shoot .308 from 7.62x51 chambered gun, but there's no problem shooting 7.62x51 from a .308 chambered gun. Well I bought a MVP LC, advertised as a .308 on the website. Well I looked at the gun when I got it and it only has 7.62x51 stamped on it. 308 isn't marked on it anywhere. According to Mossberg's website it says .308 / 7.62x51. My question is, can I shoot .308 from it safely? Is the gun ready for either caliber? Anyone with the LC shoot. 308 regularly through theirs?
  2. nitesite

    nitesite Sheepdog Moderator "Philanthropist"

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    5,554
    Great question. What does Mossberg CS say?

    I know from shooting a lot from an M1A that "some" .308 Winchester ammo isn't recommended but Springfield Armory says not to worry about .308 Winnie ammo in their gas guns.

    You obviously know based on your post that 7.62x51 is usually loaded a bit lower than some super-linear warp drive .308

    In your rifle, what do you think would be an "issue"?
  3. John A.

    John A. I'm "THAT" guy Staff Member Global Moderator Moderator

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    14,293
    worth repeating.

    This is one of those commonly argued things about on the internet. Not here, but I have seen a few near knock down drag out fights over it elsewhere.

    I am not telling you what to do, but I shoot both 308 and 7.62x51 out of my FAL. It is most certainly chambered in nato.

    Of course I checked my chamber with a set of headspace gauges before I did it though just to make sure there wouldn't be an issue and I don't use anything over 150 gr through it.

    But I truly don't think you'd have a problem, especially with a bolt action but I didn't stay at holiday inn express last night.

    All I know is most of the important Forster headspace gauges (go, no go, and field and 7.62x51 max gauges) for the most part, mostly overlap each other.

    1. GO: Corresponds to the minimum chamber dimensions. If a rifle closes on a GO gage, the chamber will accept ammunition that is made to SAAMI’s maximum specifications. The GO gage is essential for checking a newly-reamed chamber in order to ensure a tight, accurate and safe chamber that will accept SAAMI maximum ammo. Although the GO gage is necessary for a gunsmith or armorer, it usually has fewer applications for the collector or surplus firearms purchaser.
    2. NO-GO: Corresponds to the maximum headspace recommended for gunsmiths chambering new firearms. This is NOT a SAAMI-maximum measurement. If a rifle closes on a NO-GO gage, it may still be within SAAMI specifications or it may have excessive headspace. To determine if there is excessive headspace, the chamber should then be checked with a FIELD gage. The NO-GO gage is essential for checking a newly-reamed chamber in order to ensure a tight and accurate chamber.
    3. FIELD: Corresponds to the longest safe headspace. If a rifle closes on a FIELD gage, its chamber is dangerously close to, or longer than, SAAMI’s specified maximum chamber size. If chamber headspace is excessive, the gun should be taken out of service until it has been inspected and repaired by a competent gunsmith. FIELD gages are slightly shorter than the SAAMI maximum in order to give a small safety margin.

    Forster 308
    go--1.630"
    no go--1.634"
    field--1.638"

    7.62 Nato min--1.6355″
    7.62 nato max--1.6455”
    nitesite likes this.
  4. Daryll

    Daryll .270 WIN Supporter

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    On page 10 of the MVP owners manual it says:
    "Firearms inscribed 7.62mm NATO can also fire 308 WIN cartridges."

    So Mossberg obviously think its safe, otherwise they wouldn't risk a law suit if a .308 blew up in someones face.

    I had the same question, I've got my money down on a MVP LC and wondered the same thing until i d/loaded the manual and read that.

    Daryll.
    wood chucker and oli700 like this.
  5. oli700

    oli700 12g Supporter "Philanthropist"

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    good find......
  6. G8R8U2

    G8R8U2 .410

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    There are safety issues with 5.56x45 NATO and .223; but the same is not true of 7.62x51 NATO and .308... they're essentially interchangeable.

    SAAMI doesn't consider it unsafe to fire either one in rifles chambered for the other round; and every rifle and ammo manufacturer I've ever heard weigh in on the issue has said the same... at least about modern rifles.
  7. Daryll

    Daryll .270 WIN Supporter

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    It depends on which way you consider there is a safety issue with .223 /5.56

    Again, Mossberg reckon its (at least partly) ok...

    The MVP series of firearms are designed to operate with ammunition of the type
    and caliber inscribed on the barrel.
    NOTE:
    Firearms inscribed 5.56mm NATO can also fire 223 REM cartridges.
    Firearms inscribed 7.62mm NATO can also fire 308 WIN cartridges.


    Now if you have a firearm inscribed .223, and you use 5.56....???
  8. G8R8U2

    G8R8U2 .410

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    Don't do that.
    John A. likes this.
  9. wood chucker

    wood chucker .410 Supporter

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    In a nut shell lots of folks are re repeating the same wrong info.

    Oh no one is 50,000 psi and the other is 62,000 psi !!
    Hmmm not exactly.

    The big too doo about it comes from a typo in an edition of TM-43-0001-27 Army Ammunition Data sheet for Small Caliber Ammunition where it said PSI in a part of one table but used CUP in the table in earlier editions. The copper crusher and piezo systems of measurement do not inter relate.

    You see back in the stone age before piezo transducers were invented, pressures were measured using a crusher and anvil system and they weren't measured in PSI They were measured in CUP (Copper units of Pressure) The Army Ordnance Corps used this system of measuring pressure and civilian manufacturers used slightly different variation of it and the Military continued to use it long after the civilian world ( SAAMI ) went piezo.

    Again back in the stone age of the 1950's Winchester was working the experimental T65 cartridge for the Army. It would later become standardized as 7.62 NATO. Winchester released it to the public as the .308 Win. first and a few years later the Army officially adopted it.

    The big difference in the rounds themselves is compared to the .308 the 7.62 has a little less internal volume because of the heavier case. Otherwise the two rounds measure out the same. The difference in chambers is the the mil chamber is a little roomier for reliability in dirty environments while the civilian chamber is a little snugger. There's reasons for that.


    Ok then now my guess is Mossbergs engineers are aware of the difference between PSI and CUP and SAAMI and Military and civilian chamber drawings and won't steer you wrong or dangerous. Mossy being the only major gun maker left that is still family owned and run ( since 1919 ) makes me think they would hate to loose that by a stupid lawsuit for an unsafe cambering. With that in the balance, since they tell us it's safe to shoot either or in our MVP's I take it as gospel.

    My challenge to everyone is don't take my word for it. Go do some digging of your own and see what guys like Clint McKee Walt Kuleck and few others have to save on the subject. Follow the rabbit hole.
    ripjack13 and nitesite like this.
  10. nitesite

    nitesite Sheepdog Moderator "Philanthropist"

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    5,554
    Good response, Sir. Keeping a long old thread alive......
    ripjack13 likes this.
  11. wood chucker

    wood chucker .410 Supporter

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    http://www.luckygunner.com/labs/5-56-vs-223/
    It's a can of worms.
    Just because it says .223 Remington doesn't gurantee it's chambered .223 Rem. It could be chambered 5.56 and marked .223 for various reasons.
    Take the Mini-14 for one example.
    Comparing my brand new stainless Mini (1982) to my cousins early one made in 1976. Chamber cast of his measured out same as .223 Rem and mine measured out 5.56. Both rifles were marked .223 Rem. Only thing I can think is Ol Sturm Ruger wanted a bigger safety margin on account of surplus ammo or some more reliability for their rifle that was trying to compete with other self loaders for market share.

    Take exports/imports for example too.
    Importing rifles marked 5.56 to Canada and a bunch of other countries is forbidden by their laws. The difference between 5.56 and .223 chambers can fall withing normal manufacture variance. Somehow I doubt anyone checks chamber dimensions before signing off the release documents in the customs warehouses. Good thing to as it makes no real difference in new guns anyway.

    Where I set up and take notice is milsurp ammo.
    We knew milsurp ammo was a little hotter than SAAMI ammo but back then there was no green tip or 77 grain stuff.
    If it was milsurp it was all 55 grain. It shot hotter, we could hear it and measure the velocities but the primers never flattened or cratered so if we found it cheap we used it for fun or carried it in the tractor gun and saved the good hand loads with premium bullets for real shooting and busting wood chucks.

    Then the green machine ( Army not RCBS ) came out with M855 green tip and M16A2 and things changed.
    The bullet of the M855 round had a different ogive, it was loaded even hotter than the M193 stuff was and the chamber drawings were changed too. No one I know wanted to stuff that stuff in their Savage 340 unless they chamber was throated realy long. And then it didn't shoot worth a dang. It needed a good 10 twist or better yet a 9 twist to group half way decent as far as Ball ammo goes. The 55 grain M193 stuff shot better but was ho hum to begin with anyway.

    Between then and now we learned that 9 and 10 twist gave the green tip stuff its best accuracy ( as far as ball ammo goes) but the military went with a 7 twist to stabilize the new tracer which was incredibly long for its weight.


    So the moral of the story is if the manufacturer tell us it's safe to shoot either or in my gun I take it as gospel and don't loose a wink of sleep over it.
    If it's marked .223 I check it out anyway to see if it's chambered .223 or 5.56 because it's not likely to kill me but I want to know which way to go for better accuracy. Than Ball ammo still sucks in the accuracy department compared to premium fodder.

    These other fellas over at lucky gunner labs did a bunch of testing using real science and it was pretty eye opening. http://www.luckygunner.com/labs/5-56-vs-223/
  12. ripjack13

    ripjack13 Resident Sawdust Maker Staff Member Administrator Supporter "Philanthropist"

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    22,030
    More like a great post....
    nitesite likes this.
  13. wood chucker

    wood chucker .410 Supporter

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    Thank you Sir.

    What I failed to mention was for the fellas who only started reloading or shooting in the last ten or fifteen years or so keep your eyes peeled at the gun shows and whatnot for an old 12th edition Lyman loading manual and see if you can grab it for cheap.

    NONE OF THE LOADS IN IT ARE SAFE ANYMORE because the powders have changed but hot dang the manual makes for some fun and educational reading.
    And it oozes major cool factor to have vintage references on the coffee table of your man cave.
    nitesite likes this.
  14. John A.

    John A. I'm "THAT" guy Staff Member Global Moderator Moderator

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    14,293
    Oldest manual that I own is from 1982.

    There is a lot that has changed in 36 years.

    lyman manual 001.JPG
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  15. nitesite

    nitesite Sheepdog Moderator "Philanthropist"

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    5,554
    This is one of the greatest threads EVER!!!!!!!

    Thank you everyone.
  16. Defcolt

    Defcolt Copper BB

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    8
    Hi. I'm new and this is my 1st post here. Not new to shootin or reloadin though. Just wieghin in on the .223/5.56-.308/7.62 issue. I don't have as much experience with the 7.62 side, but the 5.56 side I have studied a bit more. Outside of the slight differences in chamber tolerances (the mil ones being more generous in the shoulder/neck/freebore area), the main concern is when firing mil ammo in commercial chambers. That concern is when several factors are present, ie: hot day, hot/dirty weapon, warm ammo, chamber cut on the short side of specs, etc., there could be an over pressure problem. However, the reverse is not the same, commercial ammo in mil chambers do not cause the same issues. That's the way I understand it. Perty much what John A. said up above.
    Great forum by the way, I found it lookin for MVP info for the MVP Patrol 7.62 I just bought.
    Thanks!
    wood chucker likes this.
  17. nitesite

    nitesite Sheepdog Moderator "Philanthropist"

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    5,554
    Welcome to the Forum and I encourage you to post more. You obviously have a lot to contribute. Good post Sir.
  18. CaddmannQ

    CaddmannQ 12g Supporter

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    Well this is all amazing to me, since I just started loading .223 target loads for my Savage Model 12. Several people have told me that it's no problem to put 5.56 in a .223 and vice versa, because they have done it successfully, but I can see that under certain conditions you could have a problem. I will remember to keep that chamber clean if I do this.

    My rifle is only marked ".223 Remington" but now I'm wondering how it's really chambered. Does it match either spec or is it its own animal? I suppose I could get a gauge?

    I think this gun has a tight chamber but a lot of freebore. Don't know about the shoulder yet but it seems generous. The magazine will obviously feed rounds much longer than standard.

    The typical .223 seems to be 2.260" COAL, I am able to load rounds at 2.336" which just barely clear the lands, and seem much more accurate, though I do have to tickle the rounds to get them to feed once over about 2.325".

    I have gone up to 2.435", and at 0.085" over, those engrave sharply from the lands, and shoot great, but they will not feed at all from the magazine.
  19. Daryll

    Daryll .270 WIN Supporter

    Messages:
    285

    What, you mean that my "Bible", the Speer Reloading Manual, Number 11, (1987), (the only paper reloading manaual I own) may not be relevant any more..?? :D
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  20. Tranteruk

    Tranteruk .410 Supporter

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    I have both a MVP patrol in 5.56 and another in 7.62. I have fired both those calibre's (Mil surplus) and commercial .223 and .308 without incident. As stated above the manual says you can, so I did. Given the litigious nature of the US, I cant see Mossberg saying so in print unless its safe to do so. So, lawyers can be useful for something.

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