Factory vs. Custom chamber dimensions

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by Geezer, Feb 11, 2009.

  1. Geezer

    Geezer Well-Known Member

    Oct 21, 2005
    I recently got a Shilen screw-in barrel for my Savage Model 16 in 300 WSM, and found that I had to full-length resize all my brass to get it to chamber. I did some measurements and found that fired brass from the two Savage factory barrels I've used measured .542 at the shoulder, and the Shilen barrel needed .538, SAMMI spec, to chamber.

    Is it common for factory barrels to have loose chambers? The Savage barrels shot good groups, and reloads with just neck sizing worked fine.
  2. Mikecr

    Mikecr Well-Known Member

    Aug 10, 2003
    And it's common for fired brass from one chamber to misfit another, or even the same without FL resizing.
    After a few firings in the Shilen, your brass won't even fit into the Shilen -until resized..

  3. Boss Hoss

    Boss Hoss Well-Known Member

    Nov 10, 2005
    That is the problem with "screw in fit tubes". One reason all of my dies are cut with the roughing reamer to avoid this problem. Just take this as a lesson learned.
  4. 3006savage

    3006savage Well-Known Member

    Jul 16, 2008
    My perception is that many of the custom barrels are chambered in near min spec dimensions. I could be wrong but when my buddy had two rifles done the smith claimed they were min dimension chambers to improve velocity with factory loads.
  5. J E Custom

    J E Custom Well-Known Member

    Jul 29, 2004
    I have had to set back and rechamber many factory barrels for all kinds of reasons and some would clean up with only .030 to .040 and some have needed .100 thousand + to remove an
    out of round chamber. The best factory chamber I have found took less than .008 to clean up
    to SAMMI spects.

    Head space is another problem with a lot of factory rifles. .003 or .004 thousands is with in
    spec. but can and will cause case strech and after a few times of full length sizing can cause
    case head seperation.

    So a tight chamber and minium headspace will increase case life especially if you neck size
    only for 3 or 4 times and normaly improve accuracy.

    The main differance between a factory rifle and a custom is the tolerances.( A factory rifle
    can be minimum to maximum tolerances where a custom rifle/barrel will be as near to minimum
    spects.as possible.

    Just like mass produced cars you have good factory rifles and you have lemons.