A rec.guns reader wrote:
I am told to watch for a bright ring above the belt on the magnums, others say you can measure the expansion of the web.The most important early warning of case failure is that bright ring at the juncture of the case wall and case base. This is where case stretch that is due to headspace tolerance or sizing die dimensions/setting occurs and is referred to as incipient head separation. The bright ring that I refer to is pretty recognizable in that it has a crystalline appearance and is likely to be about 1/8" or so wide. Do not confuse this with the abrupt ring that appears at the same juncture when a relatively sloppy chamber is encountered. One can check to see if incipient head separation has occurred by using a bent paper clip to feel inside the case. If it is present, an abrupt, easy to feel ridge will be apparent and these cases must not be used again.Can you reload until you see a case crack, or is it wise to retire the cases after a set number of firings?
If your cases have been loaded three to four times and have not been checked for length, it is time to do so. Over length cases can present a condition where the case mouth, upon chambering, can jam into the chamber throat. This prevents the case neck from expanding sufficiently to release the bullet as it should and can result in very high pressures. Trim to about .010" less than the SAAMI maximum.
I usually use my cases until they give longitudinal splits. These occur mostly in the neck but occasionally in the body of the case. Case life is pretty difficult to predict because there are so many variables that are peculiar to each gun/cartridge/reloader/die situation. My 7x61 Sharp and Hart (sort of an early 7 mm magnum ballistic twin) cases have well over a dozen reloads with no failures. Henry Schaffer has sent out word that he has just finished his 40th firing of 100 .38 Special cases - and has 56 cases left out of the original 100.
God Bless!
Norm