There were several folks using body dies before 1969. These were true body dies as they only sized the case body; nothing touched the shoulder nor neck. They were used on belted cases used in long range prone matches such as Fred Huntington's .30-.338 Win. Mag. wildcat he came out with in 1958. (Therefore, I think Redding as well as RCBS, Lyman, C&H and other die makers were aware body dies before 1969. I used one myself for the first time in 1968 on .264 Win. Mag. cases.) A regular full length sizing die had its top cut off at the shoulder then squared off. Its bottom cut off just above the belt clearance section where the body diameter there was about .5120" or .001" smaller than new case diameter immediately in front of the belt.
After using a standard full length sizing die (with its neck lapped out to a couple thousandths less than a loaded round's neck diameter; no expander ball used) to get the neck and body down to the right diameters as well as setting the fired case shoulder back a couple thousandths, the body die was used. That body die was set in the press so its bottom would just barely touch the belt when the press ram was al the way up. All this was done so that ridge that usually happens on new cases right in front of the belt on new cases gets sized back down to virtual new case diameters all the way to the belt. Otherwise, that ridge/step interferes with the back end of the case positioning itself the same way for every shot.
Top classified shooters winning matches and setting records had learned that new belted cases give better accuracy than fired ones resized by neck only (worst accuracy of all) or standard full length sizing dies (fair, but not as accurate as when a body die was also used. The difference was that little ridge. Once it was removed with that body die after standard full length sizing, those resized cases shot as accurate as new ones.
The 7mm Rem. Mag. rifle used to set a new 1000-yard record in 1970 (which caused Remington's sales of rifles so chambered to jump considerably) was fed previously fired cases so sized. A good friend did it with the rifle and ammo he borrowed from another mutual friend who had conducted the most intensive and complete study on fired case sizing techniques known to man. He tried neck only, neck and shoulder bumping, all sorts of partial neck sizing as well as full length sizing in addition to new cases. Using the best commercial bullets available for accuracy, they were fired from free-recoil rail guns whose match-grade barrels were chambered with minimum SAAMI spec reamers (no tight necks at all). Those bullets were also fired in factory sporting and military rifles with all sorts of chamber and bore dimensions. He didn't prep any cases (except for trimming back to length when they got too long) nor weigh powder charges. For rimless bottleneck cases, standard full length sizing dies were used but their necks were resized so expander balls (which bend case necks) need not be used. Some folks got up to about two dozed reloads per belted case and several dozed per rimless bottleneck case with such dies.
A high power rifle competitor ranked at the top having won his share of matches and set a few records along the way, he was well qualified to tell what fired case sizing tools and processes worked best for accuracy. Others with his same shooting skills also learned his tool types and use methods did indeed give the best accuracy. He was Martin Hull, Sierra Bullets' first ballistic technician who loaded and test fired virtually of Sierra's bullets for accuracy checks for so many years. Sierra still used the same type of dies these days; Redding Full Bushing Dies for cases they're made for or Redding standard full length dies for the others. The die necks are sized a little below loaded round neck diameters.
If one understands why fired cases so sized in full length dies center perfectly up front in the chamber when fired, they might understand why they've been popular with top classified high power rifle competitors since the 1950's and why the benchresters are moving in that direction these days. And there's a collet die made today that does the same thing better than those old body dies we made ourselves;
Innovative Technologies - Reloading Equipment.
