A little food for thought, below is a sectioned Winchester factory loaded cartridge case, it was fired in my 1943 Maltby and the headspace is set at just under .067.
The factory loaded Winchester case below stretched .009 in the web area when fired the first time in my Enfield that is .007 thousandths "under" maximum headspace limits.
Below the once fired factory loaded case has stretched .009 in the base web area on the first firing and will "NOT" last very long when reloaded.
Below on the left is a new unfired .303 case, please notice the location of the case shoulder of the unfired case and the two fired cases to the right. The factory loaded case on the right has only been reloaded three time at near maximum loads.
The Winchester case below when fired the first time expanded more on one side than the other, this caused the case to stretch unevenly at an angle.
Commercial cartridges cases are "NOT" designed to military specifications and were never designed to be shot in long fat military chambers. Therefore fire forming your commercial cases is critical to long case life.
The fire forming trick below was taught to me by a Canadian in the old Jouster forum. All you do is slip a rubber o-ring around the case and the o-ring will hold the case against the bolt face and prevent any case stretching in the web area when first fired.
Below the rubber o-ring holds the case against the bolt face and also as the o-ring is compressed it "centers" the case in the rear of the chamber. The centering of the case will promote equal case expansion and thus accuracy with better case alignment in the chamber.
After fire forming, the cases then can be neck sized only and the cases will then headspace on the shoulder which will hold the case against the bolt face preventing further stretching in the web area of the case.
When I fire form cases I remove the extractor to prevent it from cutting or nicking the rubber o-ring, and also help center the case in the rear of the chamber. I also grease the rear of the locking lugs to help prevent any undo wear on the locking lugs when closing the bolt on the snug fitting cases. Your headspace and rim thickness will govern the size of the o-ring but remember compressing the o-ring helps center the case in the rear of the chamber.
One reloader at Gunboards was able to reload his Remington .303 cases 32 times before the first case failure which was only a split case neck.
"NOT" one single case head seperation in 32 reloadings, thats not bad for the old Lee Enfield rifle.
