Minimum SeatingDepth 175SMK 300WinMag

Discussion in 'Reloading' started by bigbuTT, Jul 10, 2009.

  1. bigbuTT

    bigbuTT Member

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    Jan 3, 2008
    Hi,

    what do you think about the minimum seating depth with 175grs SMK in an 300WinMag.
    Is an COAL 3.570 ok? Or should I get shorter?
     
  2. johnnyk

    johnnyk Well-Known Member

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    You're only talking .23" longer than the Maximum S.A.A.M.I. Overall Cartridge Length of 3.340" which is set so that the ammo will fit in all the different rifles manufactured. As far as I know this is a "guide" for the firearms mfg's. Each rifle performs best at a particular overall cartridge length. Determining the proper length requires some test firing, as you should start by seating the bullet no deeper than good mechanical function dictates. Experimentation will allow you to determine the best seating depth for your rifle. JohnnyK.
     

  3. johnnyk

    johnnyk Well-Known Member

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    Forgot to include; the OAL length of my cartridges loaded with 180gn SMK's is 3.4715". This is running them .010" off the LaG's in MY rifle. Hope this helps. JohnnyK.
     
  4. boomtube

    boomtube Well-Known Member

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    "Is an COAL 3.570 ok? Or should I get shorter?"

    Goodness! We really can't answer that properly, we don't have your rifle to work with.

    Minimum seating depth, or Maximum OAL, will be dependant on your chamber/throat and your magazine, not any figure listed in a loading manual. The shortest of the two limiting factors will limit your Max OAL, the minimum OAL you actually use will, or should, depend on what OAL/seating depth gets you the best accuracy.
     
    Last edited: Jul 10, 2009
  5. mmmooretx

    mmmooretx Well-Known Member

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    Jul 7, 2009
    I was on the phone with one of the Sierra bullet technicians discussing their 180 gr. SMK. but they reccomended that I go to their 200 gr. Game King. In their research the 200 Gr. Game King likes to be 0.010 - 0.020 between the ogive/land engagement. I have been using the Hornaday OAL Gauge as each rifle's broach is slighetly different. Sunday I hopefully will be shooting the set that lets me know where my rifles sweet load is. Below is an excerpt from an email from Sierra. I advise you to call Sierra Tech line as they are incredably helpful.

    "If magazine length will allow doing so--normally would load hunting bullets .010 - .020 away from riflings WHILE holding bullet properly in neck; our tested oal for the 200's in .300 Winchester Magnum is: 3.340".

    We worked up H1000 from 69 to 77.5 grains with good accuracy at max. Also worked with H4831SC from 64 to 68.5 max; might try that. Didn't use any Retumbo--Hodgdon lists the powder as compressed even for the flat based bullets they tested but reasonable velocity so could be usable."