Small Base Die???

[steve4102]

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??

 

[Ol` Joe]

As far as I know they only size farther down the case wall and should have the same effect on shoulder set back as std FL dies. At any rate, the shoulder "bump" or set back can be altered with any die though simply by how deep you screw it in the press. I normally back my FL dies off until I`m only barely touching the shoulder and not setting it back nor allowing it to move forward from the expander ball drag or sizeing operation. This allows good feeding/chamber fit, and cases last longer then if the brass is over worked by sizeing way down then blowing it back out upon fireing.

What are you loading and for what rifle?
You may not need a SB die. My brothers BLR 308 and my M94 32 spcl both work fine with brass sized useing regular RCBS FL dies. I`ve talked to others that load for semi`s and most have no problem with std dies either. I`d try a regular die if you already have one before running out to get a SB you may not need. JMO..........

 

[ReloaderFred]

Small base dies only affect the size the base is resized as far down as the die can reach. As mentioned above, shoulder set back (headspace) is affected by how far the die is screwed in. Excessive headspace will cause case separations at the base from excessive stretching of the brass.

I have small base dies in .223 and .308, but never use them for my AR's or M1A's, as they don't require them. My Browning BAR also doesn't need a small base die.

You'll find more variation in headspace than you will in base diameter of chambers. For my 30-06's, I've got three different sizing dies set up for differing headspaces to prolong brass. All my M1 Garands have long headspace and my 03 Springfields have short headspace. The Browning falls in between. Brass sized for the Garands won't even allow the bolt to close in the 03's, but rounds loaded for the 03's will suffer head separations if fired in the Garands.

Hope this helps.

Fred

 

[P0832177]

From the RCBS FAQ's The Small Base Sizer Die sizes the case from the shoulder to the head of the case a couple of thousandths smaller than a Full Length Sizer Die. In certain calibers it also sets the shoulder of the case back a thousandth or two more than the Full Length Sizer Die.

 

[Peter M. Eick]

Don't buy it unless you need it. My Match M1A's need a small base or the op rod does not completely close and lock up. It is a "must" for me.