RCBS states that their SB Die sizes the base of the case slightly smaller than the full length sizer to ensure proper functioning in automatic, semi-automatic, pump, slide and some lever action rifles.

Some descriptions of the SB die from retailers state that they also bump the shoulder back farther than the FL Dies. RCBS makes no mention of shoulder setback.

Do these dies set the shoulder back farther than the FL Die??

Give em a call, 1-800-533-5000

SB's size slightly closer to the shellholder, due to a rediced radius/lead-in angle at the mouth of the die, Period, end of discussion.

There was some clown here about a year ago that was all kinds of down on RCBS because they told him that a SB was not intended (and wouldn't) size the body more or the shoulder back any further than a regular die. He just knew RCBS was wrong, cause "Bubba" down at the local gun shop knows everything.

A regular FL sizer is like a trombone at the mouth of the die and does not size to the base of the case.

A SB sizer will sometimes shave a bit of brass off the case and you can see a little curl coming off the side of the case. It sizes nearly to the shellholder.

-Spencer

Thanks everyone. I also asked this question od RCBS. This is their reply.


Small base dies reduce the base and shoulder diameters slightly.
They do not shorten headspace.


Steven J. Koch
Product Designer
ATK Alliant Techsystems
RCBS Operations
(530) 533-5191
(530) 533-7103