flat base bullets. Why?

Discussion in 'Reloading' started by 7 loader, Jun 30, 2010.

  1. 7 loader

    7 loader Well-Known Member

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    My 22-250 shoots better with flat base than boat tails. The gun is a H&R ultra varmint that I won in a lottery. It has a 24 in tube and a 1-14 twist. 50 gr nosler bt's shoot a 1.5 grp. 55 gr rem and 36gr barnes vg's
    ( both flat base) shoot a 1/4 in. grp. Is this normal or the twist rate? I am new to the 22 cal center fire
     
  2. mike33

    mike33 Well-Known Member

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    I have the same issue with a 22-250 i won also , maybe its the price we paid. I was told some guns dont like bt, i dont know but i always did have trouble getting a ballistic tip to shoot good when every else got it to work.
    mike
     

  3. BountyHunter

    BountyHunter Writers Guild

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    Most custom bullet makers will tell you that it is much easier to get a FB bullet more uniform that a BT bullet, ergo the FB bullets tend to shoot better at the shorter distances.

    BH
     
  4. Eric The Red

    Eric The Red Member

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    7 Loader, Bryan Litz, Berger Ballistician, in his book; "Applied Ballistics For Long Range Shooting" makes several comments about boat tail bullet design vs flat base. He also comments on the Nosler boat design in particular, which he believes is not an efficient design, too steep an angle. In general terms flat base bullets are marginally more accurate over short to medium distances and boat tails are more efficient beyond say 500yds I think. Sorry I don't have the book in front of me, someone may wish to correct me.
     
  5. J E Custom

    J E Custom Well-Known Member

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    Flat based bullets are best at shorter distances .And boat tailed bullets are better at longer
    distances because the BCs are almost always higher making them more stable at these long
    distances.

    If you are shooting at 100 yards try 400+ with both boat tailed bullets an flat base bullets
    and I think you will find out what bullet to use.

    I use a lot of flat based bullets for short range because of accuracy and the boat tail bullets
    are not nessary.

    A lot of bench rest shooters use flat base bullets at the 100 and 200 yard matches.

    I dont know the exact reason for this phenomenon but some say it's because the bullet exits
    the crown cleaner with less blow by at that exact moment.

    Maybe one of the bullet smiths will shed some light on the reason.

    So shoot what shoots best at the distance you plan to shoot.

    J E CUSTOM
     
  6. Boss Hoss

    Boss Hoss Well-Known Member

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    Maybe a slight correction ---100% of the COMPETITIVE short range (point blank) BR folks use flat base. I use 66.7 gr FB in my 6BR and 6PPC and 142 gr SMK's in my 6.5x284 1K BR rifle.
     
  7. Mikecr

    Mikecr Well-Known Member

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    Flat base bullets release from the muzzle cleaner, providing more consistant POI up close.
    But with any real distance in wind, less accurate but higher BC bullets will provide better results.
     
  8. tim jurczak

    tim jurczak Well-Known Member

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    Boattails are pretty popular in IBS and nbrsa 100-200 yrd benchrest right now. The Bruno 00's and Lowell Hottensteins , which are used by Tony Boyer, some of the more popular ones. The theory about the square push thru the crown is the one I hear most. Also short range benchrest bullets are shot in the slowest twist possible for the rpms the cartridge can generate. Also flatbase bullets have a pressure ring .0001 larger than shank.


    Tim J.
     
  9. MT4XFore

    MT4XFore Well-Known Member

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    I have experienced the same phenomenon. In my experience the crown of the rifle wasn't exactly concentric. Get a good crown on the rifle and it SHOULD shoot em all the same.

    Jim
     
  10. Mikecr

    Mikecr Well-Known Member

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    True, FBs & BTs could both shoot well -up close.
    But it's BC of the BTs that dominate at distance. Which is why LR competitors use heavy per cal BT bullets(whether they know it or not).
    And up close, it's nearly impossible for BT's to compete with FBs.

    There is ALWAYS a price.
     
  11. load

    load Well-Known Member

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    bullets are haunted by the same problem as muzzle crowns. if a hip of the tail of a is not concentric than gas will excape on oneside before the other forcing the tail to wag. fbs are easy to square while bts are hard to square.
    another problem with bts, at the same point as the wag, is that instead of the gasses being blowen away 90 degrees to the bullet like with a fb they are allowed to flow around the bullet creating turbulance infront of the bullet.
    fbs have their own problems like excessive drag and pressure build up behind the bullet in ss flight
    gun)
     
    Last edited: Jul 21, 2010
  12. Mikecr

    Mikecr Well-Known Member

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    In thread starters case, there is also a stability issue. 14twist is got to be the least AND worst there is for 22cal. It leaves BTs 50gr or higher marginally stable at best. Going to FBs 50gr and below, improves stability and grouping..

    Here, it's muzzle release quality that marginal twist cannot overcome.
    That's my theory
     
    Last edited: Jul 21, 2010
  13. jessedvw

    jessedvw New Member

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    i have a custom built .22-250 on a mauser action with a wilson arms barrel and the best results i have had with it is from a 40-grain v-max which is a boattail bullet, i can shoot 1/2 inch groups all day consistently with this too