very concerned nator vs. 308

Discussion in 'The Ammo & Reloading Forum' started by zkovach, Feb 22, 2011.

  1. zkovach

    zkovach Active Member

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    I bought this dpms 7.62 nato and have been asking a lot of questions about it because i like to understand my guns before i take them shooting. I asked some questions earlier about loading 308 for a semi auto. but i have been researching this and am finding out the different cup pressures between the two. Old posts here say i should NOT shoot 308 loads out of my 7.62 nato dpms. i called dpms and they said theres no differances between the two and i could shoot either. I dont place a lot of trust in the guy i talked to over the phone since he struggled to answer a bunch of my questions.

    Question: what ammo can i put through this thing. Can i put both through or only 7.62nato rounds? Are there nato recipies for reloading? i have read too many things that are condradicting each other and is making me uncomfortable.
  2. 312shooter

    312shooter Active Member

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    You will be just fine shooting either one, the problem exists when doing the opposite, that is, shooting 7.62 in a chamber designed to only shoot .308.
  3. steve4102

    steve4102 Former Guest

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  4. JLA

    JLA Well-Known Member

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    the only differenc eis pressures. The 7.62X51 nato is loaded somewhere around 55K psi and the .308 win is loaded to around 65K psi, most current mfgred weapons chambered for the .308 are proofed for the higher pressures and will be ok to shoot both, or all 3 if you count the 7.62 CETME, which is the same again loaded to 45K psi...
  5. zkovach

    zkovach Active Member

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    Ok thanks for the info guys but help me understand this. Why is it ok to shoot a 308 in a 7.62 barrel and not ok to shoot a 7.62 in a 308 barrel if 308 has more pressures I would think it would be the opposite. I'm happy u guys are helping calm my nerves by the way!!
  6. zkovach

    zkovach Active Member

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  7. steve4102

    steve4102 Former Guest

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    I have read this several times over the years and it has always come to the same end or misunderstanding, that is that the 7.62 is rated in CUP and the 308 is rated in PSI. The 50-55K CUP for the 7.62 is just about identical to the 62K psi for the 308 Win. Or Not?
  8. JLA

    JLA Well-Known Member

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    shoot now you got me confused... Google time...
  9. RandyP

    RandyP Member

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    So let me understand this...... you DON'T trust the info given to you over the phone by someone at the company that makes the thing....but you WILL rely on info from total strangers on an internet forum?

    Interesting decision making process.
  10. JLA

    JLA Well-Known Member

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    I cant find anything on that steve, Most of the load tables I have dont list a working pressure for the nato. You may be right. and the DPMS man done told the OP that hes ok to shoot both, so I really dont see the issue. Would be nice to see it in writing from a reputable source tho eh?
  11. polishshooter

    polishshooter Active Member

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    I wouldn't be worried at all with any MODERN rifles...much less a DPMS.

    But if you want to shoot an old Cetme, an old SMLE MII or MIIA, but ESPECIALLY one of the small ring 1916 Spanish small ring mausers rechambered from 7mm to 7.62 and advertised as ".308" I would pay attention...or any old military bolt gun with an INSERT that "allows" them to shoot .308....

    I owned a 1916 Mauser once but couldn't bring myself to shoot it with ANYTHING:D and sold it, and for my Ishapore SMLE MArkIIA I ONLY shoot surplus 7.62 NATO in it...guys CLAIM they shoot .308 Win in theirs, but I keep thinking, 1964? India? Milsurp NATO is good enough for me!:p
  12. steve4102

    steve4102 Former Guest

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    The only thing I have is Quickload. It lists everything in PSI. Both the 308 and 7.62 Nato are listed at 60K.
  13. zkovach

    zkovach Active Member

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    If you were in on the conversation you would understand it was a young guy and he had no definate answers for me. When i asked him about the ammo and he said i SHOULD be fine red flags went off. When he said there are no difference between the two, red flags were raised again. When i asked him if theres no difference why do you have barrels labeled .308 and barrels 7.62 i knew i couldnt trust any info given by him at that point.

    As far as the total strangers on this forum, yes i do trust them. They have answered many questions that experts at companies and books have not answered. They have helped me out of many binds. Just because someone works at a company doesnt mean they know anything about they're products!
  14. zkovach

    zkovach Active Member

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    I just remembered i had a lyman book downstairs and looked at it and they post 308 win ans have 7.62 in () behind it.
  15. steve4102

    steve4102 Former Guest

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    Yup good call, my Lyman 48 list the 308, 7.62x51 and 7.62 Nato as the same with interchangeable data.
  16. JLA

    JLA Well-Known Member

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    good enough for me!
  17. zkovach

    zkovach Active Member

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    Yeah me too! Thanks again for the reassurance guys!
  18. Warith

    Warith Member

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    You all got scracting my head on CUP vs PSI so I went and looked at some books.

    Here is what I found:

    .308 winchester 150grn bullet with H4895 listed in CUP 50000 Lymans
    .308 winchester 150grn bullet with H4895 listed in PSI 59000 Lees

    so what realy is the defferance?

    Here is what one book says about it:

    "Presently there are four principle methods of measuring breech pressure. The oldest is the copper crusher system. This involves having a test barrel with a hole in the chamber. The hole is fitted with a piston. A small copper cylinger rest on the top of the piston and below the anvil. When the gun is fired the expanding gas pushes the copper cylinger and crushes it against an anvil. The ballistician measurs the new length of copper cylinder and looks on a table to determine the pressure. This used be listed as the Pressure per Square Inch (PSI). Now it's called Copper Units of Pressure(CUP). For lower pressure laods Lead Units of Pressure is used. This technique is smilar to the CUP system except lead is used."

    Notice he said: "This used be listed as the Pressure per Square Inch (PSI). Now it's called Copper Units of Pressure(CUP)". This would make me think they are the same however when using the same powder with the same bullet you get 7k defferance in numbers they cant be the same.

    Now I am realy confused.
  19. bluesea112

    bluesea112 Active Member

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    I own a DPMS .308, and I reload using 43.3gr (maximum) of IMR 4895 with 168gr bullet. I have never had any signs of high pressure.

    Interesting to note, the Hornady manual also has a chart for the .308 Service Rifle. I assume they mean .308 Nato. The maximum load using IMR 4895 on the Service Rifle chart is 41.9 gr. with a 168gr bullet.

    The manual says that a max load of IMR4895 produces 51,200psi. There are other powders on that same chart that show pressures around 58,000, so I am clearly in the safe zone even with a powder thrower that fluctuates a grain or two each time it throws powder.
    Last edited: Feb 25, 2011
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