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Thread: Is there any benefit to short barreled 7.62 nato?

  1. #11
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    Uhh... Have you seen the Noveske Leonidas? We gotta jerk off to something....
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  2. #12
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    I remember reading somewhere about an HK G3 variant used by the SAS that had a 9 inch barrel. I can only imagine how stupidly loud that must have been. Probably difficult to suppress.

  3. #13
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    The people the 13" SCAR H was designed for have access to 7.62x51 and not .300BLK.

  4. #14
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    Quote Originally Posted by Bolt_Overide View Post
    I've seen this bandied about a few times by others, and I just cant get my head around it. Is there something I'm missing?
    Got it bro!! many threads all why/how it will not work. Try looking for ways to make it work---heavy/lite projectile vs reduced/compressed loads, different combo powder burn rates w/ differ weight and types of bullet. And that's just the ways to tweek ammo for desired results. Maybe integral supp. is the ticket, meh maybe?? To tell truth, I have no Idea at all (know very little about 308 AR platform). Would like to see it work tho.

    2nd--Who's to say what exactly are acceptable results? A lot of people (myself included) think that 7.5'' 556 AR's are unacceptable/range toys. But Then some say within 0-50ish 7.5'' length 556 round (with selective ammo) will produce acceptable results. Maybe find out all vel/ft lbs/etc of various 556 loads out of 7.5, 10.5, 12.5 length barrels and ratio/compare/crunch them too various length 308 lengths. Who knows might see why its not useful or....

    3rd--This is America! All its gotta do is A)Go bang B)Look bad ass. If all a SBR 308 is; is a range toy. Make it the most Kewl-nst uber toy (read about a "loudener" muzzle dev., slap that puppy on there) on range. Not because its viable, but because its fun damnit! Ask not why you should have SBR'd 308, but why you shouldn't?? If it makes ya happy and doesn't hurt nobody else, then Rock Out With C@ck Out brah... On side note; SBR 308 with custom/crazy suppressor setup, sportn exotic hand-loads(provided could be done safely), would keep ya busy for while and be conversation piece at range.. But so would the obscenely loud one. Just some thoughts.
    Last edited by lunchbox; 08-18-13 at 02:57.
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  5. #15
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    an 11 inch .308, while being much louder and less efficient than a .300 AAC, is still going to be faster with a heavier bullet.

  6. #16
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    Quote Originally Posted by PathfilmsNZ View Post
    an 11 inch .308, while being much louder and less efficient than a .300 AAC, is still going to be faster with a heavier bullet.
    Having experience with .308 pistols this is very true. But also much more recoil as its less efficient than the mid capacity cases like the BR family.

    Also will have more muzzle blast/flash unless loading dialed in with faster powders. Which also has small impact on recoil as well... Powder burning outside the barrel does not add to velocity, but did add to recoil.

    Sent from my PRC-104 using phonetics

  7. #17
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    Quote Originally Posted by PathfilmsNZ View Post
    an 11 inch .308, while being much louder and less efficient than a .300 AAC, is still going to be faster with a heavier bullet.
    What velocity are you getting from 11" .308 barrels with what projectiles?
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  8. #18
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    Quote Originally Posted by Suwannee Tim View Post
    A good way to think about this is to describe the barrel length in calibers which is the barrel length divided by the bullet diameter. For example a 14.5 inch 5.56 mm barrel is about 65 calibers long. A 16 inch 7.62 mm barrel is about 52 calibers long. For standard rifle cartridges barrel length below 50 calibers and certainly 40 calibers gets you well into a regime of diminishing returns. By this reasoning a 16 inch 7.62 barrel is a short barrel.
    I agree, but not necessarily by your computations. I look at velocity. A 16" tube on a .308/7.62NATO weapon will give you approximately 2500-2600fps with standard 147-150gr FMJ loads. Heavier bullets (obviously) will generate less juice. While it is not really comparable to a 7.62x39, being heavier and faster, it is not what I would prefer in ballistics from a .308 given the blast and recoil you will encounter from the shorter tube.

    Most chrono results I have seen indicate that if you want to go shorter than a 20-22" barrel in .308 that 18" seems to be the best compromise. Very little speed lost at 18".
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  9. #19
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    Quote Originally Posted by ABNAK View Post
    I agree, but not necessarily by your computations. I look at velocity. A 16" tube on a .308/7.62NATO weapon will give you approximately 2500-2600fps with standard 147-150gr FMJ loads. Heavier bullets (obviously) will generate less juice. While it is not really comparable to a 7.62x39, being heavier and faster, it is not what I would prefer in ballistics from a .308 given the blast and recoil you will encounter from the shorter tube.

    Most chrono results I have seen indicate that if you want to go shorter than a 20-22" barrel in .308 that 18" seems to be the best compromise. Very little speed lost at 18".
    175gr M118LR and AB39 run at about 2520-2530 f/s out of 16" barrels.
    20" barrels add about 50 f/s.
    Adding a suppressor adds about 30 f/s.
    Jack Leuba
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  10. #20
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    Powder burning outside the barrel has zero affect on recoil. Powder exiting under high velocity from the muzzle has a large affect on recoil. It adds to the thrust, same as the gasses exiting the nozzle of a rocket engine.

    The difference in velocity between a 300 BLK or the 7.62x39 and the 7.62x51 isn't but about 100 fps when the barrels are very short. The 308 would be using twice the powder for very little gain. From SBR length barrels, the 300 BLK would be doing about the same job more effeciently using lighter, smaller ammo and with less recoil due to using only half the powder.

    Suwannee Tim's ratios are dead on. It's all about the case volume/bullet diameter/barrel length ratio and why a small capacity case is better for pistols and a large capacity case works better in longer barrels. It's also why the 300 BLK will operate a carbine length gas system reliably but not a middy
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