PhillipM

Originally Posted by Parashooter

First off, you need to know exactly what you're measuring. Here are the SAAMI cartridge and chamber specs for .30/06 -Note the measurements from base of case and chamber (bolt face) to the .375" datum on the shoulder. Case = .2.0526" to 2.0456"; chamber min. 2.0487", max 2.0587". Since none of the dimensions you're quoting are within these specs, we have to conclude that either your measuring tool isn't providing an accurate reading at the .375" point on the shoulder or all of the cases you've measured (2.022" to 2.036") are significantly short.This leaves us with information that is useful only in relative terms and is missing the critical dimension of a case fired at normal pressure (which will reflect the chamber dimension fairly closely.) All we know is that the head/shoulder measurement of your fired reduced-load cases shows a .006" reduction from the original sized dimension and is reduced a further .008" on sizing.Perhaps what you're missing is really some critical dynamics -1. When a rimless case is chambered forcefully, its head/shoulder dimension can be reduced significantly simply by the chamber acting as a sizing die. Furthermore, the primer's force acts to push the case farther into the chamber - "sizing" it some more. Under normal pressure, the case expands fully, re-seating the primer and stretching to fill the available space in the case. At significantly reduced pressure (as is generated by your 4759 loads), the case doesn't expand fully and/or completely re-seat the primer - leaving the head/shoulder dimension more or less reduced from what it was before chambering and firing.2. When sizing a case in a full-length die, the resulting head/shoulder dimension varies depending on (among multiple other factors) the dimensions of the fired case. Larger/longer cases produce more strain on the press and die, resulting in significant flex and a sized case of longer head/shoulder dimension than when a smaller/shorter case is sized in the same die. The press and die are, after all, made of somewhat elastic materials that stretch and compress less when lighter resistance is encountered.It's not uncommon for F.L. sizing dies to be made with a significantly shorter head/shoulder dimension than is appropriate for most chambers. (This reduces the number of customer complaints from novice reloaders who don't well understand press/die flex dynamics.) Experienced reloaders often adust sizers to produce cases that will just fit in the intended chamber. This is best judged not with an imprecise gauge but with the actual rifle in which the loaded ammunition will be fired (feeling for resistance when chambering a sized case with a stripped bolt).If readjusting dies for minimal sizing isn't sufficient, cases previously used in reduced loads that have experienced a reduction of less than about .015" in head/shoulder length can be "salvaged" simply by firing with a normal load. If the reduction and resultant cartridge end-play is greater than ~.020", it's can be worthwhile to fireform them at moderate pressure (~40Kpsi for .30/06) with a thin lubricant film to prevent chamber adhesion and consequent stretching at the web/wall transition. (Few well-made classic military rifles are threatened by the ~10-20% increase in "bolt thrust" resulting from carefully lubed cases, but care should be taken to avoid excess lubricant and consequent hydraulic neck lock.).(Chamber cast was used to extract broken case #1, too tightly stuck for conventional tool.)