of cases that far exceeds 5% obviously do exist. And, we all know how much harder it can be to resize a poorly lubri- cated case. Therefore, using any resiz- ing die adjustment that does not result in the shellholder always abutting the base of the die, regardless of required resizing effort, we easily can imagine shoulder placement variations of up to 4/1000-inch. This is exactly what one experimenter found when he measured a large batch of same-lot 308 Winchester cases that had been fired in the same gun and that he had resized in this manner. Therefore, resizing cases using
Cross-sectional sketches of cases during resizing with conventional shellholder (left) and with Redding +10 Competition shellholder (right): This clearly shows why using a taller shellholder during full-length case resizing will result in greater case-body length and therefore less functional headspace of the resulting chambered case. Indicated here is a standard shellholder (left) compared to the Redding +10 shellholder (right) with all else being equal (same die, same shellholder-to-die abutment, etc.)
installed that case in the shellholder and resized it, using my normal tech- nique for press operation except that I stopped with the ram fully raised. I then measured the gap between the top of the shellholder and the bottom of the die: 15/1000-inch.
While Redding makes a tool that would have allowed me to measure changes in case shoulder placement with significantly greater precision, that tool requires use of a reloading press and to do the measurements reflected in this study I would have had to use two presses. I did not have the energy to set up a second press – perhaps next time. Meanwhile, the RCBS Precision Mic is a fine tool and provided adequate precision to prove the thesis of this study.
Page 136 Winter 2013
This means that the force re- quired to resize that case was sufficient to stretch and deform the press and compress the ram and die base a total of 15/1000-inch. More important, this means that a case-to-case variation in toughness (relative to necessary resiz- ing force) of only +/-3.3 percent would result in a variation in case headspace length of fully 1/1000-inch. And, as most of us are well aware, the force required to resize cases from any given batch often varies enough that we can easily feel the difference. Because it is physiologically difficult for most of us to reliably feel a variation of less than 5%, case-to-case variations in required resizing force within any given batch
the unscrew-the-sizing-die-just-a-little method necessarily introduces signifi- cant case-to-case variation in functional headspace. And, all serious shooters know that consistency is key to good accuracy; inconsistency and good accu- racy are an unlikely pair. Therefore, this monumental source of inconsistency cannot possibly contribute to accuracy. I will not claim that the old method has no value for any chambering for use in any gun. I will say that a far better method exists. IDEAL OPTIMUM
FULL-LENGTH RESIZING Redding offers the Competition
Shellholder set for exactly this purpose. In the standard set, the five shellholders are progressively thicker between the surface that supports the case head and the top of the shellholder, in 2/1000-inch increments. So, the handloader can ad- just the full length sizing die to solidly abut the shellholder while full-length resizing all cases and still leave the case body either 2, 4, 6, 8, or 10 thousandths inch longer than would occur if he were using a standard shellholder. (On spe- cial order, Redding makes even taller shellholders for various common case rim sizes; I have a set for the 30-30 that runs all the way to +20/1000-inch.) (In any bottlenecked case with a significant shoulder, regardless of nominal headspacing, it always is best to move headspace control to the case shoulder. Those shooting bottlenecked belted or rimmed cases usually will see improvements in case life and accuracy with this approach. In many belted-magnum chamber- ings when using a typical full-length resizing die, the gun chamber is so much longer than the die chamber that pre- cisely moving headspace control to the
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