probably a stupid question,,how do you "not allow" the case to stretch on the first firingChambers and resizing dies vary in size so you could pick the best brass but if your chamber is on the plus side and your die is on the minus side you could still have problems.
Meaning the answers you get here are not written in stone and can even vary between manufacturing lots of cases.
Below a example of .223/5.56 cases, the Federal case on the left has a thinner flash hole web than the Lake City case on the right. The thicker flash hole web adds radial strength to the base of the case and makes the primer pockets last longer.
On the belted case the diameter and thickness of the case above the belt and the brass hardness also has a big effect. I would also look for the highest rated cases "BUT" proper fire forming and not allowing the case to stretch on the first firing is also very important also.
probably a stupid question,,how do you "not allow" the case to stretch on the first firing
I jam bullets all the time when firing virgin brass in my Ackley chambers to control headspace with great success. I also agree with JE's post above that a properly cut Ackley chamber should control headspace via crush fit at the neck-shoulder junction. I have found that the case head to neck-shoulder junction dimension can vary quite a bit from brand to brand and even lot to lot, so fireforming with a jammed bullet is an additional measure of headspace control. Jamming bullets in general does increase pressure, so adjust the powder charge accordingly.No disrespect, but this is very bad advise. This can result in excessive pressure. Also, would be related to bullet seating depth, not brass fit in a chamber
Reloading 101: Fireforming CasesNo disrespect, but this is very bad advise. This can result in excessive pressure. Also, would be related to bullet seating depth, not brass fit in a chamber