RCBS SB Dies???

Discussion in 'Reloading' started by Kevin R, Mar 31, 2010.

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  1. Kevin R

    Kevin R Member

    Jan 6, 2009

    I got a set of RCBS SB (short Base) 223 dies on a trade.

    I have read that the SB dies are for semi's,pumps and full auto's and not recomended for bolt guns. They say that they push the neck down slightly and size differently then the FL dies. I have compared them with my FL dies and don't seem to see or find any measurment difference and the brass fits in my bolt gun the same??

    Does anybody know what the difference is and can they be used with a bolt gun??


  2. phorwath

    phorwath Well-Known Member

    Apr 4, 2005
    I believe SB stands for small base, not short base.

    The SB dies are designed to resize the brass casings to a smaller diameter in order to allow more reliable feeding into the chambers of the semi-auto actions or pump actions, where the additional resistance of a tighter fitting cartridge into the chamber could result in failed feeding.

    The reason they would not be recommended in a bolt action rifle is that the added down sizing of the brass is not required in bolt action rifles, and the greater the brass is worked down during resizing and then expanded during firing, the lesser the brass life. You'll get fewer reloads because of the extra work hardening of the brass cases with the SB dies.

    A lot of guys get away with the normal resizing dies even with the AR15s. I'm using the standard RCBS dies in my AR15 and have not experienced any jammed actions so far. Haven't shot it alot yet, but so far, so good. If I start experiencing feeding malfunctions, I'll buy a Redding SB body die and reduce my reloaded .223 ammo so it can feed into the chamber with greater ease (a looser fit in the chamber).
  3. rg1

    rg1 Member

    Jun 30, 2008
    Small based sizing dies don't push the shoulder back more than a full-length sizer. The shoulder sizing should be the same for both sizing dies. The small based sizer sizes the body of the brass a little more than a full-length. Actually small based sizer dies sizes the brass closer to the size of factory ammo brass while full-length sizing dies don't quite size the brass down to the same as factory ammo. Small based dies work the brass a little more and usually are not needed for bolt action or semi-auto rifles but there would be no reason that you couldn't use it if you wanted for your bolt action. Just works the brass more than necessary.