Lead angle question. 1°30 or ??

Discussion in 'ELR, Ballistics & Bullets Board' started by FatBoy, Sep 20, 2017.

  1. FatBoy

    FatBoy

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    Most of my reamers have had a lead angle of 1° 30. My current 284Lapua match reamer has .206" freebore with a 1° 30 As well but I had it made in 2005, when you either shot 168s or the 175SMK. Since then, I see some of the new reamers listing 1° 47-33. I'm not familiar with this, can someone enlighten me?

    I haven't shot 7mm since '06 so I send JGS a dummy round for a new no-turn reamer for an upcoming project. They will be calling me in the next week or so to approve the print. I want to make sure I'm up to date on what is shooting. Plan is to use the Berger 180 hybrids, which didn't exist in '05. I think I have the body dims down as they haven't changed for the Lapua brass and I have set freebore off the a chamber I know to shoot but I want to make sure the lead angle I pick is right for the current crop of bullets.

    Any advice from someone who's BTDT lately.

    Thanks,

    Chris
     
  2. Alex Wheeler

    Alex Wheeler Gold $$ Contributor

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    The saami lead angle is 47 minutes 33 seconds. Its a hair over 3/4 degree per side. It works very well by the way. 1.5 degrees is standard now but theres pros and cons with different angles. If your not looking to experiment stick with 1.5. I have done different angles, dont be afraid to, you may just learn something :)
     
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  3. FatBoy

    FatBoy

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    Thank you, Alex. I am going to Google the conversation to make sure I understand the differences you listed. I'm unclear if 1° 30 = 1.5 or if there is a difference so time to do some Googlefoo and do some match learning ;)
     
  4. Alex Wheeler

    Alex Wheeler Gold $$ Contributor

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    Degrees minutes and seconds, 60 seconds in a minute, 60 minutes (MOA) in a degree
     
  5. brians356

    brians356 Gold $$ Contributor

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    Browsing through SAAMI drawings, the newest cartridges (Nosler) have the following leade angles denoted:

    26 Nosler: 3.0 deg.
    27 Nosler: 1.5 deg.
    28 Nosler: 3.0 deg.
    30 Nosler: 1.5 deg.
    33 Nosler: 2.0 deg.
    35 Nosler: 3.0 deg.
    36 Nosler: 1.5 deg.

    I'm curious how these angles were chosen for a particular cartridge.
    -
     
  6. M-61

    M-61 "Quis Separabit" Silver $$ Contributor

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    As Lance said to Vincent in PULP FICTION:

    " I'm kinda curious about that myself...."
     
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  7. Alex Wheeler

    Alex Wheeler Gold $$ Contributor

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    Well a larger angle will erode slower. If they put a 1.5 in a 26 Nosler I can imagine how fast the throat would move.
     
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  8. brians356

    brians356 Gold $$ Contributor

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    So what's to choose between 27 and 28 that warrants 1.5 vs 3.0 I wonder? Seems arbitrary.
    -
     
  9. BoydAllen

    BoydAllen Gold $$ Contributor

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    As you all probably know, there are 360 degrees in a circle. Each degree can be divided into 60 minutes, and each minute into 60 seconds. This sums it up pretty well.

    I found this a the top of results of of a Google search for "degrees minutes and seconds notation"
    "The first method divides each degree into 60 minutes (1° = 60'), then each minute into 60 seconds (1' = 60"). The symbol for degrees is ° , for minutes is ', and for seconds is ". "

    So, a degree and a half is one degree thirty minutes, and a 20 MOA (minute of angle, or in math minute of arc) base is angled a third of a degree 20/60= 1/3.
     
  10. FatBoy

    FatBoy

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    I went with 1°30 on the new reamer. Thank you all for the assist.
     
  11. Alex Wheeler

    Alex Wheeler Gold $$ Contributor

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    I do not know why the designers did what they did. It could be as simple as two different people designed those reamers. I have a 3 degree in my 28 noslers, they shoot better than a case that big should.
     

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