243AI or 6mmAI m

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by Tikkamike, Jun 12, 2011.

  1. Tikkamike

    Tikkamike Well-Known Member

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    I am place Ming a new build and I'm leaning toward a 6mm of some sort. I am thinking 243 AI or 6mm AI. I like the added velocity of the 6mm AI. But the brass offerings of the 243. so I'm asking for opinions on the 2 or even other good short action long range calibers. Its going in a single shot small shank savage action. Its going to be used for deer and antelope. Rocks. Steel p dogs that sort of thing.
    So please all input wanted.
     
  2. B23

    B23 Well-Known Member

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    IMO, a 6-284 would be better than both. Lapua brass. More case capacity which really shines with the heavier long range bullets and best part of all, no fireforming.
     

  3. Tikkamike

    Tikkamike Well-Known Member

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    Very nice idea! Donyou think I would Have issues ejecting a loaded round with a 6-284 on a short action?
     
  4. CPGfan

    CPGfan Well-Known Member

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    A 6-284 is way better suited for a long action, but building them on a short action can be done. Trevor with CPG build me one and it shot fantastic. I would lean towards a 243AI as they are much better suited for a SA. Trevor has a great reamer for one, every one I have been around that he has build has shot in the high 2's to low 3's if the shooter can do his part. I am shooting the 105 right at 3270 out of a 26.75" tube and most of the 6-284's he builds only shoot 3280-3350. You are giving up quite a bit of barrel life with the 284.
    As far as fireforming goes, Trevor can build you a hydro form die out of your resize die to where you never have to fireform at all. When you form the cases they come out about .005" over a fired case, so then you just run them through your resize die and bump them back to .001ish" smaller than a fired case and you are good to go!!. Here is how my last Trevor 243 AI shoots. Would be worth a trip down the street I would guess.
    [​IMG]
     
  5. Trickymissfit

    Trickymissfit Well-Known Member

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    the Savage action is a little longer than a Remington, and this makes things easier. I'd go with the 6mmAI without a secound thought. But you might also consider using a 6mmAI reamer, and set the headspace with a .243AI gauge. This gives you the .243 case length but with the better 6mm neck design (you'll still have to use 6mm brass). The 6mmAI barrel will last longer than a .243AI barrel, but most of all the longer neck will help you keep the base of the bullet out of the shoulder area of the case. As it should be. I'd also be thinking about a 1:8 twist barrel for really long range bullets.

    The 6AI barrel will have a much longer barrel life than the 6/.284 if that matters. Both rounds are overbore, but the 6/284 is getting excessive. Precision Shooting ran a test a few years back, and found the 6AI was almost a 100FPS faster, and handled the long VLD's better than the .243/.284 case did. Might also want to think about a 6Vias
    gary
     
    Last edited: Jun 13, 2011
  6. Franklin

    Franklin Well-Known Member

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    Tricky, how in the world is the 6mmAI barrel going to last longer than the 243ai?
     
  7. Tikkamike

    Tikkamike Well-Known Member

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    I was just going to ask the same thing.
     
  8. buckbrush

    buckbrush Well-Known Member

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    I think the longer neck helps out.
     
  9. Trickymissfit

    Trickymissfit Well-Known Member

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    case design is better due to the much longer neck length. This helps to keep the turbulence point out the the throat. The .243 neck length is too short to start with, and after fire forming cases ends up another .030" to .040" shorter. If you have a CAD program on your PC, then make a drawing of the shoulder neck area. Then extend the shoulders to where the cross in the neck. The 40 degree shoulder helps out a lot with the .243, but the T.P. is still too far out in the neck. It also seems to help with brass flow. Now if you draw the 6mmAI case and extend the shoulders to where they cross, and you'll see the difference
    gary
     
    Last edited: Jun 13, 2011
  10. Franklin

    Franklin Well-Known Member

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    Okay, this makes some sense, but how much life are we talking and is it even worth worrying about? Out of the 2 I'd still pick the 6AI. Thanks for the input on neck lengths.
     
  11. Tikkamike

    Tikkamike Well-Known Member

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    thats interesting tricky. Does that mean a 300 win is harder on a barrel than a 300 wby? I understand there is still heat index for a given powder and all that jazz that goes into calculating barrel life but theoretically a win would be harder on a throat than a wby? or am I wrong?

    Also I am going to throw the 6x47 in the mix. See how many votes that little guy gets. I think its a cool little cartridge
     
  12. CPGfan

    CPGfan Well-Known Member

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    The 6x47 is a fantastic cartridge as well. Can't go wrong with it as long as you are ok will velocities below 3200 shooting H Extreme powders. I know that some guys are getting more shooting R17 but it is not proven yet to be temp stable,
     
  13. Trickymissfit

    Trickymissfit Well-Known Member

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    I talking almost double the life; plus the advantage of handeling the very long bullets better
    gary
     
  14. Trickymissfit

    Trickymissfit Well-Known Member

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    Never heard any serious compairsons made between the .300's, but I'd pick the Weatherby. with similar throats shooting big heavy bullets the .300WBY really starts to come into it's own. The 25 degree shoulder angle really hurts the Winchester, while the Weatherby computes to about 47 degrees. Thus putting the T.P. right in the middle of the neck.

    I like the 6mmx47, but like the 6BG that much better. It's pretty much a 2.04" case reamed with a 6mmAI reamer. Shoulder length comes out at about 1.552".
    gary