Chamber and dies vary in size and nothing is written in stone.
For a semi-auto the full length resized case body should be .003 to .005 smaller than its fired diameter. This allows the case to spring back from the chamber walls and extract reliably.
My standard Lee full length .223 die will size the case smaller in diameter than my RCBS .223/5.56 AR series small base dies.
I buy bulk Lake City once fired 5.56 and 7.62 cases and size them the first time with a small base die. Thereafter I measure the fired case diameter in "MY" rifles and decide which die to use.
Bottom line, you are dealing with brass spring back after sizing, the brass hardness, your chamber diameter and your dies diameter.
Lake City 5.56 and 7.62 brass is harder than commercial .223 and .308 brass and this effects how much the case expands when fired.
Chambers and dies have plus and minus manufacturing tolerances so nothing is written in stone. And measuring the case body after firing and sizing will tell you a great deal.
Below a link on .223/5.56 brass hardness, and soft brass was one of the many reasons for the original M16 jamming problem.
How Hard is Your Brass? 5.56 and .223 Rem Base Hardness Tests « Daily Bulletin
Below Forster makes three dies for the .308 to cover all sizing needs.
For a semi-auto the full length resized case body should be .003 to .005 smaller than its fired diameter. This allows the case to spring back from the chamber walls and extract reliably.
My standard Lee full length .223 die will size the case smaller in diameter than my RCBS .223/5.56 AR series small base dies.
I buy bulk Lake City once fired 5.56 and 7.62 cases and size them the first time with a small base die. Thereafter I measure the fired case diameter in "MY" rifles and decide which die to use.
Bottom line, you are dealing with brass spring back after sizing, the brass hardness, your chamber diameter and your dies diameter.
Lake City 5.56 and 7.62 brass is harder than commercial .223 and .308 brass and this effects how much the case expands when fired.
Chambers and dies have plus and minus manufacturing tolerances so nothing is written in stone. And measuring the case body after firing and sizing will tell you a great deal.
Below a link on .223/5.56 brass hardness, and soft brass was one of the many reasons for the original M16 jamming problem.
How Hard is Your Brass? 5.56 and .223 Rem Base Hardness Tests « Daily Bulletin
Below Forster makes three dies for the .308 to cover all sizing needs.
