No, if the brass is too thick, you risk exceeding the maximum allowed O/D. In a tightly chambered barrel, there may then be insufficient clearance between case neck walls and the chamber hampering bullet release and seeing pressures rise substantially.meles meles wrote:Hmmm, the brass will have gone thick at the neck, thus will hold the bullet too tight and give an increased pressure? So we needs to shave a fraction off the neck to compensate?
As an example, PT&G's chamber drawing for its 6.5X47 Lapua CIP Chamber reamer specifies 0.292" plus or minus one thou'. Typical Lapua 47L brass has neck walls 0.0125-0.0130" thick and Lapua / CIP specify a maximum neck wall thickness of 0.345mm = 0.0136". So if you had a box of cases all at the maximum and a chamber at PT&G's minimum tolerance with the usual a little over the nominal 0.264" bullet diameter - say 0.2644-inch, you get a cartridge neck O/D of:
0.2644 + 0.0136 + 0.0136 = 0.2916" against a minimum chamber neck diameter of 0.2910". So, on paper with this cartridge, if the tolerances run the wrong way, you have nil clearance and potentially serious over-pressure problems.
Even with everything at nominal dimensions, the round has an O/D of 0.290 v a chamber of 0.292", only 1 thou' clearance at any single point around the neck. Make the brass up by reforming 308 and it'll likely have neck thickness values well above Lapua's maximum and in in this case the resulting rounds (perhaps fortunately for the user) probably won't chamber. (There is always Murphy though with a strong right arm and failing that a mallet to make things go where they'd rather not!)
There is nothing wrong with reforming 308 for lots of cartridges, although I'd baulk at doing it with 243 with so much good and affordable brass around for the cartridge from very competent manufacturers. It is essential though to measure the wall thickness of necked-down cases either on the walls themselves with a tubing or case-neck micrometer, or by seating a bullet and measuring the O/D.
