Primer Guide

Discussion in 'Reloading' started by mshaner, Jun 4, 2011.

  1. mshaner

    mshaner Well-Known Member

    Dec 28, 2010
    Evening Gang,

    I'm making pretty good progress along the reloading learning curve and have now two conservative in nature and one that tries to find the edge of things seeking out ultimate accuracy.

    That being said, I can't reach either of them tonight and can't find any clear and concise info on primers.

    Question: How does one go about classifying a caliber as "large" caliber vs. a "small" caliber? I love charts but can't dig one up.

    For example: I'm using Winchester Large Rifle primers in my .300 WM but am now getting ready to load up some .308's...from what I can tell a .308 falls into the large caliber category, but hey, I'm relatively new and would rather not put the wrong primer in the cartridge.

    Hopefully, this is not a broadly discussed topic and someone has a nice little chart that I can reference.


  2. jimbires

    jimbires Well-Known Member

    Mar 16, 2008
    it's the diameter of the primer .if I remember right small rifles are about .170 and large are about .210 . there is enough difference that you won't screw up . yes a standard 308 will use large rifle primers . some aftermarket brass for the 308 is made for use with small primers . Jim

  3. Browninglover1

    Browninglover1 Well-Known Member

    Jan 10, 2011
    Jimbires is right that there is enough of a difference between small rifle and large rifle primers in terms of diameter that it is impossible to screw it up. However, there are Large Rifle Magnum primers and standard Large Rifle primers.

    For the 300 win mag you're shooting you should be using Large Rifle Magnum primers according to all my load books and just a standard Large Rifle primer for the 308. The difference between the Magnum and the Standard primer is how hot they burn. The Magnum primer has a hotter/bigger blast to help light bigger amounts of powder (especially in the cold).

    If all you have are Large Rifle Magnum primers they should work just fine in the 308. I've loaded them in a 308 and 270 before, because it's what I had on hand, and both worked fine but I did need to reduce my powder charges to get rid of excess pressure signs. Just reduce your starting loads by a few grains and work up watching for pressure signs.
  4. Reloader222

    Reloader222 Well-Known Member

    Jun 4, 2010
    Go to the following links for interesting data:

    For photo's on primer burning go to:

    Also go to: Primers And Pressure
    Last edited: Jun 5, 2011