ShrinkMD, I got into a mindless thread on another forum, the thread had to do with brass flow or stretch, it was more than they could handle, seems "IT WAS IN THE BOOK" therefore brass flows forward 'PERIOD' and the brass came from the web?, which is part of the case head and below the case body, I called it the T'AIN'T because it taint the head of the case and it taint the body of the case and the top of the web is the bottom of the cup and the web extends down to the top of the primer pocket. My thinking? if brass flowed forward, where are the skid marks on the outside, after all 50,000 PSI pushing out on a tapper works on a pony brake, slips and anchor pins (Duo-servo) and there are no growth rings that would allow counting the number of times a case has been fired. I am thinking brass receives a shock in the form of 'hammering', hammering the case body against chamber wall with X PSI flattens the brass.
Flatten brass? At the Market Hall Gun Show the purchaser if a custom rifle built by a friend of 53 years claimed the rifle had head space issues, arrangements were made for the rifle to be returned to the shop for inspection, I did not get involved until, I noticed he carried the case in a sling, I ask to see the case, upon inspection I ask the owner of the rifle if the case he handed me was the only case he had and the only case he fired and reloaded etc., he did not understand the question so I explained his case was coming apart by extraction from the chamber or the case had been fired so many times the case could not be full length sized, and I said the case, in my opinion would not survive neck sizing, I offered to form cases that would enable him to start over and allow him to spread the strain of being fired over a greater number of cases, my friend heard part of the conversation and offered a remedy, he sent his customer to a third party, 'man of few words' with the instructions he was not to be told what I said or be told who built the rifle, the case was carried in the sling to the third party, the third party pulled the case apart without effort, then measured the thickness of the case body, he asked the customer if he only had one case, he explained .0025 is OK for paper but not OK for case wall thickness. The customer returned, irritated, it seems he was proud of the case and did not think someone would rip it apart, the man of few words was not told not to, and being a man of few words did not ask. The customer changed his mind about head space, and I wondered, was he a bench rest shooter, or did he get the case from someone that got all the possible use out of the case , I do not know, no skid marks, no growth rings, it looked to like the case was flattened against the chamber wall.
Head of the case and shell holders, some listing call for two shell holders because the extractor groove is not the same for all cases for one caliber AND not all shell holders are identical, I have old shell holders that will not allow a case that has been fired with signs of high pressure to be inserted or older Super X cases plus one South American surplus 7X57. In an effort to accommodate all cases the shell holder is not a close or tight fit, Lee is loose, RCBS is not as loose, for the most part a .011 feeler gage can be inserted between the bottom of the case and shell holder when the case is inserted, good to know when sizing cases for short chambers, the Lee shell holder for 30/06 has a gap of .017 thousands between the shell holder and bottom of the case, advantage/disadvantage, if the case is allowed to float and align when the ram is raised, the case is self centering, if the case is too tight to align the shell holder must be precision or adjustable, or be able to float on top of the ram.
If there is any truth to the information above, always consider a case that will not fit the shell holder has been hammered causing the case head to upset, this is the first sign of excessive pressure, the only sign recognized is loose primers and always blamed on soft brass, and very few measure the diameters of the flash hole, primer pocket and case head before and after firing.
they determined brass flow was the reason for case head separation because the brass flowed from the T'AIN'T to the neck AND that was the reason a case trimmer was necessary, and they said 'IT'S IN THE BOOK', I do not claim to have read THAT book but claim a case can go beyond insipient case head separation to catastrophic case failure by compressing the head of a case beyond yield pressure, crushing, hammering or upsetting the case head can expose the body of the case to an unsupported condition, if the case is locked to the chamber and the case head moves back, to me the brass stretched at the T'AIN'T, and the case body is hammered causing the wall to thin and flow (flatten) it upsets is enough to flatten the case head and the brass at the T'AIN'T yields, the T'AIN'T gets thinner, with enough upset the case body could be exposed to an unsupported condition, at this point the problem has been upgraded to catastrophic failure from insipient case head separation caused by brass stretch at the T'AIN'T, reducing head space by reducing all that case travel cuts down on thinning of the brass between the case head and body.
F. Guffey
