Hope this was just a typo :0
Bassman
When you pull the trigger on a firearm you release the firing pin and it moves forward and hits the primer. The firing pin proceeds to push the cartridge forward until the rim, the belt or the shoulder of the case contacts the chamber. The cartridge then goes "BANG" and as pressure starts to build it pushes the primer out of the primer pocket. As the pressure builds further it will push the case back against the bolt face as pictured below.
On lower pressure cartridges like the 30-30 if you follow modern reloading manuals the primer will always protrude from the rear of the case and only the primer will be touching the bolt face. This is called headspaceing on the primer because the rear of the case never touches the bolt face. In the older reloading manuals for the 30-30 the max load was higher than it is today and the 30-30 primer would be flush with the rear of the case.
On a rimmed cartridge if you measure your rim thickness and the amount the primer is protruding from the rear of the case you have your total headspace. Thus if the primer is protruding from the rear of a 30-30 case it is headspacing on the primer.
And if your were not wasting your time eating popcorn when you worked up a load you would see the primers protruding from the rear of the case until enough chamber pressure was generated to push the case against the bolt face as the load is increased.
And if you had bothered to read the link I posted in my previous posting
"Re: 336 primers back out?" you would have seen this person was five grains over max and the primers were still backing out of the case.
Now remember this, reloading manuals are not written in stone and all loading data varies, the two charts below represent two .223 cases that vary 1.8 grains of H20 in case capacity. They also vary 6,000 psi in chamber pressure with the same charge of 25 grains of H335 powder. And this is just
"ONE" variable in all your reloading component possibilities that effect chamber pressure and working up a load, and not counting the firearm itself.
So do us all a favor and put down your popcorn and make up a workup load for any rifle you have starting at the suggested starting load and working up to maximum and "LOOK" at your primer as you do this.
Now look at the chart below for the .223/5.56, keeping in mind the max rated pressure for the .223 and 5.56 is 55,000 psi. The factory loaded .223 cartridge on the left was only loaded to 49,000 psi, "BUT" the military 5.56 on the right was loaded to 55,000 psi.
Bottom line, factory ammunition is very seldom loaded to max pressures for the same reason the loading manuals are listing lighter loads. In today's world there must be enough room in the chamber for the cartridge to fit along with the company lawyer. And there are a lot of very old and well worn 30-30 rifle still being used today and a chain is only as strong as its weakest link.
Now read the Google links below and don't get any popcorn butter on your keyboard as you educate yourself.
why do primers back out
https://www.google.com/#q=why+do+primers+back+out
Civilian Marksmanship Program (CMP) reloading forum below (they are the ones who sell our M1 Grands to us)
Primer set back on reloads. (.30-06, M1)
Post #6
"Primers that "back out" after firing usually indicates the chamber headspace is longer than that of the cartridge. However, this condition normally occurs when the chamber pressure is on the low side; low enough that the case "adheres" to the chamber and the primer backs out to meet the bolt face. If a cartridge's headspace is less than the chamber, with a full pressure load, then the case will stretch to match that of the chamber, and the primer will not back out. If you increase your powder charge, this condition should not happen."
http://forums.thecmp.org/showthread.php?t=51804
