300 NM Imp Freebore (225gr ELD M) and body taper

Discussion in 'Big Stuff -- 6.5mm, 7mm, 30 Cal' started by 300SALRH, Feb 13, 2018.

  1. 300SALRH

    300SALRH

    Joined:
    Mar 21, 2016
    Messages:
    13
    I'm currently trying to get all information together for a 300 NM Imp reamer. Would appreciate assistance with two dimensions that I haven't yet finalised, namely the freebore and body taper.

    I'm planning on shooting the 225gr ELD Match. What is the reamer dimension from the base of the bullet to where it touches the lands? If I subtract the boat tail length of 0.16 (what my research indicate), I will have the reamer length from the bearing surface boat tail junction to the point where it touches the lands?

    What type of throat erosion (length) can one expect after 250 rounds?

    I have order both the unfired and fired 338 Norma case holder for my Wilson case trimmer. Wilson said that I'll be able to use the unfired case holder for virgin 300 NM (despite the difference in taper between the two cases). If I want to use the fired case holder for fired case, should the taper in my reamer be the same as that of CIP/SAAMI 338 NM reamer? The taper is still between the taper of numerous 300 NM improved reamers that used for comparison. I asked Wilson about that but they just wanted to do a custom case holder.
     
  2. Bart B.

    Bart B.

    Joined:
    Jun 25, 2012
    Messages:
    697
    I estimate about .001 inch of throat erosion down the bore for every 15 to 20 shots fired.
     
  3. 300SALRH

    300SALRH

    Joined:
    Mar 21, 2016
    Messages:
    13
    Thanks Bart!
     

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