300 blackout bullets

Discussion in 'Big Stuff--7mm, 30 Cal, .338+' started by remingtonman, Mar 22, 2020.

  1. remingtonman

    remingtonman

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    Question for you gun gurus, I have a 300blkout that I currently shoot .308 diameter bullets out of, would it be ok to shoot 7.62x39 bullets that are .310 in diameter through the blackout or will I get excessive copper fouling and abnormally high pressures?
     
  2. P1ZombieKiller

    P1ZombieKiller Gold $$ Contributor

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    I have no idea the answer to your question other than.... CAN... or SHOULD?

    I would NEVER shoot a different caliber bullet through a barrel that it is not designed for it.
    I assume those 7.62 x 39 bullets are 150ish to 175ish bullets? And a box of them are $20? maybe $25?

    Is it worth it???????
     
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  3. DukeDuke

    DukeDuke

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    you will get higher pressure for sure
    .308 bullets are usually cheaper than .310
     
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  4. Lone Hunter

    Lone Hunter Silver $$ Contributor

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    I agree with zombie killer. Why? Buy a 7.63x39 and use them for it. Out of the .300 BLK use .308 bullets. No need for a reason to create problems.
     
  5. Bill K

    Bill K Silver $$ Contributor

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    I would say no, that few thousands in diameter will raise pressure in the 300 blk. And it would also cause you seating issues with the case sized for the 308 diameter dies. More than likely you would possible split cases trying to squeeze the .311 bullet into the .308 neck.
     
  6. remingtonman

    remingtonman

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    Thanks for all the info guys. Everything you all have said is what I have been telling my brother in law who was pondering the idea of trying the “cheaper” .310 diameter bullets in a 300blkout
     
  7. dellet

    dellet Gold $$ Contributor

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    Can, and has been done by many people. There are a couple of Hornady bullets, 123 grain and I think a 110 Zmax that are cheap as a bulk bullet. When you could not find .308 bullets for any price, these were used.

    Neck diameter loaded, is a bigger problem than bullet diameter down the barrel. Easy to end up with less than .002” neck to chamber clearance. Just load light.

    Best thing to do is run them through $25 Lee bullet sizing die. Probably takes about 800-1000 rounds before you start saving money. But if it all you have......
     
  8. Zero333

    Zero333

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    You might not even be able to chamber the rounds because the freebore diameter of the 300blk is right around .309"
     
  9. FrankG

    FrankG

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    Your asking for problems!

    I wouldn't do it!

    One as has already been pointed out....pressures will jump big time. Even a bullet at .3090" diameter in a chamber with a .3088" to .3089" freebore diameter the pressures jumped 6k psi on a max loaded round and that was with a bullet only .0001" to .0002" bigger than the chambers throat. Now just think of adding another +.001" bigger bullet diameter.

    Second has been pointed out that because if the chamber was cut to true 300BO dimensions the throat's freebore is .3090". The .310" diameter bullets will cause chambering issues and not to mention make the neck of the brass get bigger as well. That will be another area of concern.

    Later, Frank
    Bartlein Barrels
     
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  10. FrankG

    FrankG

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    To correct my previous post. I mentioned that that pressure jumped 6k psi. That is incorrrect. I found my notes from when we went thru all of this. Pressure jumped on the low end 13,800psi to a high of 16,400psi.

    All because of a .0001" - .0002" difference on freebore vs bullet diameter.

    Later, Frank
    Bartlein Barrels
     
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