why not a 80-95 gr. 7.62?

Discussion in 'The Powder Keg' started by Hahn, May 27, 2008.

  1. Hahn

    Hahn G&G Newbie

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    Why is'nt there a light 7.63X39??...say about 80-95.gr. area. Seems that would be a nice hot round and still heavy enough to push it's way around.
    Seems something like that would be lower recoil improving accuracy, fast, and would still have punch. It would seem to be a nice all purpose round. Am I wrong?? Maybe they are all ready out there and I have'nt seen them yet.
     
  2. Well, . . .

    this sort of thing can be a bit more complex than you might think.
    First, you need to establish the muzzle velocity desired for this bullet weight in the gun you plan.
    Second, you must study the rate of twist of the rifling in the existing gun you have.

    Accuracy will be a matter of having a rifling twist to properly stabilize the bullet weight you desire at a muzzle velocity you wish to produce.

    Quite often the existing rifling twist for a generally accepted bullet weight and muzzle velocity will not work with lighter weight bullets.

    So, a good idea just may not catch on with the industry.

    If you really wish to pursue this there are many wildcatters out there who might want to work with you.

    Good luck if you pursue this project.
     

  3. muzzlebreak

    muzzlebreak G&G Newbie

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    80gr. 7.62X39mm ammo

    Hello Hahn, theres a guy on Gunbroker right now selling ammo called "Magsafe" thats 80gr. 7.62x39mm. He claims it travels at 2750fps. It's $37.00 for 12 rds. though!! -(if I read right)-

    I'm 'muzzlebreak btw.. I've lurked here at times but saw your question and finally joined so I could answer ya. I like ya'lls forum, I've learned a lot and look forward to being part of it.....MB
     
  4. Hahn

    Hahn G&G Newbie

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    Welcome aboard Muzzlebreak...thanx for the ammo lead but that price 124.gr sounds better all the time. lol

    And thanx Nathangdad for your input. lots of things consider...more than I thought.
     
    Last edited: May 29, 2008
  5. AnaxImperator

    AnaxImperator G&G Newbie

    Nathangdad is right, and there are a lot of other factors that decide whether combat rifle rounds are effective of not.

    Some of this you already know. When a round leaves the muzzle, it is imparted with spin from the twist of the rifling. This spin stabilizes stabilizes the bullet, increasing accuracy. Rounds and rifles are designed around each other, and creating a bullet far heavier/lighter might mean the rate-of-twist given by the rifling is inadequate (or too much), as Nathangdad mentioned.
    Modern combat rifle designers decided on a rate-of-twist for their chosen rounds that would provide an acceptable amount of accuracy, yet still be somewhat unstable in flight. That instability means when a round impacts flesh, it begins to tumble quicker. Spin a bullet too fast and it won't tumble. So with rifles that have a fast twist-rate, some rounds are designed with cavities behind the nose of the bullet, increasing the tumble-effect when hitting a human target. Lightweight bullets will expend their energy fast after entering the target, and cannelures on the round cause it to break apart when the unstable round begins to tumble. This is the principal behind the M855 (5.56x45mm NATO Ball) cartridge.

    How the 7.62x39mm FMJ or HP round would perform if lightened significantly would depend on it's ability to tumble upon target impact. Using a light 7.62x39 round with a very large cavity behind the nose would cause instability and exacerbate tumbling, even if the rifling's rate-of-twist is too fast for a light bullet. Following the M855 Ball formula by adding cannelures might cause the round to break apart when it tumbles, and make up for the lessened fpe (foot-lbs/energy) expended inside the target because of a less massive bullet. Scoring the inside of the jacket before swaging the round may make it split apart/explode under centrigual force upon target impact.

    When the M16 was first designed, it had a fairly slow rifling twist-rate, and that coupled with an unstable, small caliber, high-velocity round, it caused very dramatic & deadly wounding effects when first introduced. However, later iterations of the M16 increased the twist-rate and those lightweight bullets began to simply zip through targets, and thus the cannelure was added.
    But leave it to the Europeans to try and screw up a fairly effective design; they insisted on further increasing the twist-rate to make wounds from the 5.56x45 NATO more "humane". Unfortunately for the enemy, the Euro's plan backfired. When the small & light Ball rounds were spun up very fast, the increased centrifugal force on the bullet caused them to literally explode when entering a body-cavity.

    So even a very light rifle round can be effective; it just has to be tweaked a bit to retain lethality. But I wouldn't bet my life on MagSafes. Do a search on MagSafe's effectiveness.... I saw some pretty disappointing x-rays of the aftermath of a MagSafe impact (with still breathing subjects).
     
  6. just_a_car

    just_a_car G&G Newbie

    It's actually kind of funny you asked this, Hahn. I'm actually wondering the exact opposite question. Why can't they have heavier rounds in the 7.62x39 round?

    I mean, they have 240 and 250 grain bullets for .308, why can't they have something similar for the LARGER diameter .311 bullet?

    I haven't seen anything larger than maybe 154 or 174 grain for .311 caliber bullets.

    The reason I want something that heavy is I want to work up some sub-sonic 7.62x39 loadings for my AES-10. Since the velocity is fixed at a maximum, the only way to increase energy is to increase the weight of the projectile.
     
  7. AnaxImperator

    AnaxImperator G&G Newbie

    I'd think that a heavy 7.62x39 round would be resistant to tumbling and fragmentation (or expansion, if a HP is in the cards), although you wouldn't have to worry much about max. effective range & drop if you're developing a sub-sonic cartridge. So I'd work at maximizing that tumble and/or fragmentation with a JHC (jacketed hollow cavity), JRN, plain spitzer (flat-bottom), or by scoring the jacket.

    A .308 Win / 7.62 NATO projectile has a larger case behind it, so a heavy round can be pushed faster with more (or different burn-rate) propellant without approaching the case's limits. To send a heavy 7.62x39 round downrange and maintain velocity/max. effect. range, I'd think the case would be struggling to contain the added pressures.
    Or maybe not....
    Since the 7.62x39's case is steel, it might handle a hotter load a lot better than a brass case.

     

  8. Keep looking buddy, they make them. I've got lots of the 186 FMJ and some 215gn soft points (8Z ?). Search for them under .303 Brit
    (Unfortunately for you I live in the UK, otherwise I could have given you some)

    PS. Wideners sell a 200gn bullet.
    ""SE2226 .311/303 200GR GRAND SLAM BULLET $17.70 PER 50 RD BOX ""
     
  9. Hahn

    Hahn G&G Newbie

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    Hey all!! FYI...ammoman.com has 44gr. 7.62x39. It's for indoor short range shooting. It's a fast round, 3000-3500 fps. Effective and accurate to 200 yrds.
    Now invision this round as an 88-95 or even a 100 gr. bullet. No reason it would not be a very nice all purpose round that would rival any NATO 5.45 or 5.56 or (whatever they are) round for speed, accuracy, lower recoil and effectiveness.
    What ya think?? Of course you would'nt want the plastic tip on it but rather fmj.
     
    Last edited: Jun 7, 2008