Why 7.62 or 5.56 or .308?

Discussion in 'Long Guns' started by Tim, May 7, 2019.

  1. Tim

    Tim I am....an enchanter. Staff Member Benefactor Charter Life Member

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    Why not 7mm or 5mm or .300....

    I'm not talking about nomenclature, I'm asking about the actual dimensions. Why did 7.62mm become the standard when it could have been 8mm or 7.5mm?

    Is that couple thousandths really impactful?
     
  2. Catfish

    Catfish E Pluribus Mendacium Charter Member Supporting Member

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    It dates back to at least 1891 when 7.62x54r came about. I'd guess it has more to a lot to do with machinery and institutional momentum.
     
  3. B00ger

    B00ger Das B00G Charter Member Supporting Member

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    Wow, this is a major subject. To really get into it you would have to study the history of each round, where they came from, what their original platform was and so forth.

    My "back of the napkin" answer is that intermediary calibers were adopted by nearly all militaries as combat became more and more a factor of volume of fire and which side could keep it up the longest. It became much more effective for an infantryman to double the ammo he could carry in the field while not adding additional weight. Especially in theaters where resupply was not as quick. When my dad was in the army, he was issued an M14, and I believe his load out was 4 magazines and one in the rifle. That's only 100 rounds...standard. Today the "standard" load out I believe is 210 rounds for the M4 style rifles, or more than double. Add on to that extra mags carried and extra ammo carried on stripper clips ect, it means the average soldier can keep going for more than twice as long. A number of vets I have talked to who served in Vietnam were often shooting where they thought the enemy was and as mentioned above, the contact was decided by who could keep firing the longest.

    Another small point to consider is that during the Cold War NATO and Warsaw Pact countries were often supplied by either the US or the USSR, so naturally the 5.56 and the 7.62 became the "standard". Growing up one could sometimes tell the "good guys" from the "bad guys" based on if they had an AK or not. So, there is an element of expedience when outfitting multiple fighting forces from around the world to all share the same equipment and cartridges. So, once a caliber was adopted, it became a matter of economy of scale.

    I have found it interesting to watch the re-adoption of alternate rounds in recent years as the battlefield has again changed. In Afghanistan some soldiers were struggling with the range of engagements, so from what I was told, the M14 has been brought back for some designated marksmen since it added range capabilities. And the military has spent a lot of time and money coming up with new rounds that made the range less of an issue. Whether it be performance at long range in Afghanistan, or short range house hopping in Iraq.
     
  4. Tim

    Tim I am....an enchanter. Staff Member Benefactor Charter Life Member

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    That's a lot of words that don't say why it couldn't have a 5.5mm cartridge instead of 5.56. =)

    What I'm hung up on is why didn't the designers use nice round numbers to make things more easier? Is that 100th of a MM the tipping point between "this works" and "that doesn't"?
     
  5. B00ger

    B00ger Das B00G Charter Member Supporting Member

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    It’s why I started by saying you would need to google each for their history.

    It for some of them, they are round numbers. 7.62 is just another was of sayin .30 cal. and so forth.




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  6. 11B CIB

    11B CIB IG: HandloadsAndHoldovers Staff Member Charter Life Member

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    But not every 7.62 round is really 7.62

    7.62x54r is more like .311-.313 rather than the 7.62x51 being .308

    So the plot thickens even further
     
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  7. WadeWatts

    WadeWatts Shameless Glock Fanboy

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    5.56 is not really 5.56 mm.

    74F7A6E1-1829-4D8E-89D4-F3DFD939DD46.jpeg


    The names of many rounds are misnomers. It can be very confusing.
     
    Last edited: May 7, 2019
  8. BatteryOaksBilly

    BatteryOaksBilly A SHOOTER Benefactor Life Member Supporting Member

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    7.62 is just another was of sayin .30 cal.


    Unless it ain't...



    Sent from my iPhone using Tapatalk[/QUOTE]
     
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  9. B00ger

    B00ger Das B00G Charter Member Supporting Member

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    Because if they were all freaking exact then Lee, Dillion, and RCBS couldn’t sell as many dies. It’s pretty freaking obvious guys.


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  10. Dale Flinchum

    Dale Flinchum Active Member

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    The bore size is usually the measuring point for military purposes: 5.56mm = 0.219, 7.62mm = .300.
     
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  11. Railsplitter

    Railsplitter Klugscheißer

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    Why? Because 'Merica!
     
  12. Railsplitter

    Railsplitter Klugscheißer

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    I really don't know other than to guess that someone, somewhere started calling the bullet by its diameter minus the depths of the lands (.308 - (2 x .04)) = .300 = 30 caliber. Then .308 became 7.62 once we decided to go metric. But even that doesn't hold true for all other calibers. I read a good article on this awhile back, but can't remember where.
     
  13. Howland

    Howland Your daily dose of snark

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    I thought the side that wins the war gets to write the history and name the cartridges.

    Oh wait, that only applies in theaters where you make mushroom clouds. Never mind.
     
    Last edited: May 7, 2019
  14. JBoyette

    JBoyette Well-Known Member Vendor

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    On the 7.62mm question.

    The 8mm mauser was under contract by Springfield to be the next US Military Rifle. They "powers at be" wanted a American Rifle, not a super high quality German design. So came along the 1903. One of the changes was a from a 8mm ".314" to a ".30" caliber.

    Once the action was changed the OAL stayed and we got the 30/06 1903 Springfield.

    The .30 caliber bullet dies from lake city plant for WWI, WWII rolled over to the new 308 win round shot in the improved M1 Grand, the M14.

    Since NATO was a new idea, to standard all calibers to make supply chain issues simple. NATO dumped all calibers but two.
    7.62x51mm NATO "30 cal .308win"
    50 BMG

    This is why the G3, FAL, M14 and such domanated battle fields until 1982 when the 5.56mm was approved for nato use.

    So the question is simple. We had a ton of machines producing .30 cal bullets and a ton of .30 cal barrels in surplus.

    The .223 Rem caliber was a stop gap because the M14 is and always was a turd of a service rifle.
     
    Last edited: May 7, 2019
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  15. Railsplitter

    Railsplitter Klugscheißer

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    blasphemy.jpg
     
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  16. nbkky71

    nbkky71 Active Member

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    Perhaps it had to do with finding a balance of strength, stability and performance as they relate to projectile diameter. Perhaps it was trial and error...
    • 5.3mm was too light and disintegrated at high velocity
    • 5.8mm was too heavy and shed velocity too quickly
    • 5.6mm had too much yaw
    • 5.56mm was the perfect balance
    Whatever the original reason, I suspect it's been lost to the sands of time
     
    Last edited: May 8, 2019
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  17. B00ger

    B00ger Das B00G Charter Member Supporting Member

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    I’ve heard Boyette’s opinion mirrored before, but my old man loved his and preferred it over that new plastic pop gun.


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  18. Windini

    Windini Plank Charter Life Member

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    7.5mm did happen: 7,5 x 54 French. Because French.
     
  19. JBoyette

    JBoyette Well-Known Member Vendor

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    The M14 is the 2nd shortest life of a service rifle in American military history.

    People can say all the love for it they want but it sucked, alot. The myth of the M14 being accurate is well documented in CMP Service Rifle matches. Its not fyi
     
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  20. WadeWatts

    WadeWatts Shameless Glock Fanboy

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  21. Howland

    Howland Your daily dose of snark

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    Thanks. Now I know what the "shoulder thing that goes up" is. No wonder DiFi has her panties in a knot. That makes it extra killy. It's probably even against the Geneva Convention.
     
  22. Schattenreiter

    Schattenreiter Member

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    [​IMG]


    Then on top of all that you have 28, 20, 16, 12 and .410.
     
  23. Pack72

    Pack72 Member

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    Was 7.5 the point at which the cartridges were no longer damaged when the rifle was dropped?
     
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  24. Ikarus1

    Ikarus1 Avtomat Krishna-kov

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    Pretty sure 7.62 Nato pre-dates .308 Win as a cartridge. Of course it's basically the same thing but yeah...it was a .mil cartridge first.

    The history of .223 Rem and 5.56 is exactly the opposite. Either way.....the chambers are the main difference, not the brass powder and bullet
     
    Last edited: May 8, 2019
  25. Combat Diver

    Combat Diver Well-Known Member

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    Disagree on the history. The US started with .30 cals in the 1890s when in 1892 we adopted the Krag series of rifles. The .30 US Army (aka .30-40 Krag)used a .308 inch bullet. Case was rimmed. Lessons learned after the Spanish American war lead to the adoption of the Springfield rifle. Biggest take away was the adoption of the stripper clip and Mauser action over the loading gate and weaker Krag action. We saw the advantages of the 7x57mm Mauser, not the 7.9x57. We paid Germany royalty money for it. First Springfields were chambered for a .30 cal Model of 1903 cartridge (7.62x64mm), later to be shortened and use a splitzer bullet. It became known as the .30 US Government Model of 1906, aka .30-06, .30 US Springfield or 7.62x62mm. Germany would have its own continued development of the 7.9mm case. Bullets went from .318" 7.9mm J to .323" in the 7.9mm JS. We won't be on the receiving end of the 7.9mm until WWI. Even in 1916 during the Mexican Expedition against Poncho Villa we went up against the 7x57.

    There was another smaller and shorter lived cartridge that came out and adopted by the US Navy/Marines in 1895 as the 6mm Lee Navy using the Winchester straight pull rifle Model of 1895 Navy. Gun only seen action once during the 1900 Boxer Rebellion in China. The .220 Swift case is based off the 6mm Lee Navy.

    CD
     
    Last edited: May 8, 2019
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  26. Tim

    Tim I am....an enchanter. Staff Member Benefactor Charter Life Member

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    25 posts in and nobody can tell me why 'they' didn't use round numbers. It is truly a mystery that may only bug me, but it does. That's my cross to bear. =)
     
  27. Downeast

    Downeast Happy to be here

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    Could it be that the original parent case had something to do with it? Did they use the metric system in the 1800's? Even today a lot of our cases have an ancestry all the way back to the old British H&H and Rigby cases. 30 caliber, 32, , 333, 416, for example. They necked them down to 30 caliber (later 7.62), 32 caliber (8 mm), and so forth. It may not be the bullet, but the history of the case. ??????????
     
    Last edited: May 8, 2019
  28. Combat Diver

    Combat Diver Well-Known Member

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    Because it didn't come out even. I did use .30 cal. Never truly had even numbers even with black powder, they were rounded to the nearest .01", ie .36 cal or .44 cal cap and ball used .375 and .454 balls. The 1863 .58 cal muskets used .577" balls. Numbering system was never exact, interesting history however. Also different measurement systems and how to measure. Russians used a old lini or line, hence the 1891 Mosin Nagant rifle was a 3 Lini caliber.

    When the US started our unit of measurement was the inch or English measurement, not metric. Hence no even 5, 6, 7mm etc. Even if you took the common 9mm handgun round there are various bullet diameters of .354-.364" Even then not everyone uses the same 9mm.

    CD
     
    Last edited: May 8, 2019
  29. JBoyette

    JBoyette Well-Known Member Vendor

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    Also you get odd measurements from older guns. Some had a heck of a time from a caliber of inside or outside lan measurements. Since the invention of button rifling this went away fir the most part.

    Cut rifling still has its ups and downs. :)
     
  30. AR10ShooterinNC

    AR10ShooterinNC Happy to be here

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    So where did Winchester come up with the 270, it's .277. I really could see them using 7mm, .284, 7mm was a popular bore size in Europe.
     
  31. JakeH

    JakeH Active Member

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    Nobody really knows anymore. It’s not a nice round number away from 7mm or .30 cal, it’s not evenly splitting the difference in between 6.5mm and 7mm, and there really wasn’t a .277/6.8mm prior to it other than some prototype Mauser had worked on for China. It is however, 10% less than .308 so perhaps that had something to do with it?
     
  32. AD43576

    AD43576 Well-Known Member Charter Member Supporting Member

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  33. THE PUNISHER

    THE PUNISHER Member

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    Isn’t the 7.62x54 and other rounds measures the groves (312) and we yanks measure off the lands(308)?
     
  34. dalek

    dalek Member Supporting Member

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    I think not only the Russians do that; remember the 7.5x54 and the 7.5×55 use our .308 bullets just fine.
     
  35. georgel

    georgel Behind Every Blade of Grass

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    Gee Tim, got a little OCD going on? Personally, I love this kind if history. A little science, a little logic, a little tradition, a little ego, and a lot of politics. That's how we got what we got.
    There used to be a show called How the States Got Their Shapes and it was the same way. Why aren't all the states uniformly shaped? Let that one annoy you for a while. Great history on that show, by the way.
     
    Last edited: Jun 12, 2019 at 1:46 PM