Boat tail or flat base

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by BigDaddy0381, Dec 3, 2007.

  1. BigDaddy0381

    BigDaddy0381 Well-Known Member

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    Question,
    Dose a boat tail bullet burn a barrel out faster than a flat base bullet?


    There was a few guys arguing about it at a gun show last weekend.Thought i would ask and see what ya'll had to say.
     
  2. AJ Peacock

    AJ Peacock Well-Known Member

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    There has been supposition of that idea, based on some research of laminar flow and the flame being orthogonal to the plane(s) of the base of the bullet.

    I'm of the opinion that since the flame is 'different' between the flat base and boat tail bullets, that the throat erosion should be 'different'. Whether the difference is noticeable in the real world and whether its worse for flatbase or for BT bullets???

    There are those on this and other forums that will state as fact that 'IT DOESN"T MATTER'. I think flat statements like that don't add to the collective knowledge (unless someone else is willing to jump in and argue the opposing viewpoint).

    My personal opinion (came to me in a caffeine induced stupor, so nobody should argue too vehemently with it), is that for a instant, as the bullet is leaving the neck of the cartridge (BT's will leave a little sooner), that the heat of the powder will hit the throat an itsy bitsy (technical jargon) bit more than for a similarly weighted flat base bullet. Added to the paper on laminar flow that I read, I'd say BT's will lead to a tiny bit more throat erosion. But I wouldn't bet much on it (if there was a way to prove it), but I wouldn't bet anything against it ;-)

    Just my personal, unsupportable, not worth argueing about it opinion.

    AJ
     

  3. Steve Shelp

    Steve Shelp Well-Known Member

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    BigDaddy0381,
    That above statement from AJ is so very true. And lets say this posts goes on for 2 years and has 1000s of replies. In the end it will still boil down to the above statement. In theory there is a difference, but in the end does it really make a difference in barrel "life". no

    To expand on this a little, myself and a couple close friends who are big into long range BR shooting have done many experiments and one of our latest is shooting flatbase bullets in 600 and 1000yd BR competition. It a long story as to why, but something we wanted to try and test out.
    Anyway, the test started out great. The first 6.5 140gr FB bullet design started shooting like a house-a-fire and won the first match out. We had a lot of success and no problems for awhile. Time goes by and these bullets started comping apart in flight and I ended up with several DQ for insufficient impacts on the targets to be scored.
    When we ran into the bullets coming apart problem we talked with another long range competitor who is also a mechanical engineer by trade and has his own Oehler M43 permanetaly setup in his backyard shooting range. He informed us of some of his own experiments with his own 6mm FB bullets that came apart and showed comet tails on 25yd targets. He took a lot of 6mm FB bullets that would come apart in flight and cut a 3 degree boattail on the bback of them and they quit coming apart as often. He used the same barrel, Lot# of bullets, powder, everything on his own range and was able to reduce the number of blowups by simply cutting a 3 degree?? taper on the back of the existing bullet jacket.

    That right there says there is a difference in heat transfer/generation between boattail and FB bullets under controlled test conditions. But as was pointed out above what does it really mean in the overall life of a barrel? I keep exact records of all of my competition rifles. I can't tell the difference in barrel life between the two bullets. The throat goes out first in a barrel and I beleive it has more to do with temperatures and pressure more than anything mecanical in the bullet.
    Or to state it another way... what is the quickest way to burn out a barrel? Shoot hot loads at high velocity or increase your sustained rate of fire without a cool down period! And you can do both of the above with or without boattail bullets.

    Steve
     
  4. Boss Hoss

    Boss Hoss Well-Known Member

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    For under 300 yards I use FB period for the long range stuff the BT is the best bet... I shoot 1k BR and have never found any difference in tube life --borescope verified...
     
  5. BigDaddy0381

    BigDaddy0381 Well-Known Member

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    I really can't see how are why it would make much defferance with ether.but it was fun listening to them go on and on and on about it.

    THANKS for the info
     
  6. goodgrouper

    goodgrouper Well-Known Member

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    There is no practical difference between the two in barrel life. Other factors influence barrel life way beyond any measurable amount of boattails vs FB.
     
  7. BigDaddy0381

    BigDaddy0381 Well-Known Member

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    This was my thoughts also.