My plan, if I ever start reloading .223/5.56 was just not sort brass, but load it all to .223 specs. This guy says load 5.56 to 5.56 specs. So if I do as planned, am I at risk?
The European CIP considers the .223 and 5.56 to be the same cartridge and use different pressure taking methods. The major differences between the .223 and 5.56 are the twist rate and throat length.
Almost all military rifles have a slightly different chamber but a M1 Garand is still a 30-06. "BUT" when we adopted a NATO standard for ammunition we use metric designation for the case and use the European pressure taking methods.
The .223 and the M193 5.56 are loaded to the same U.S. standard of 55,000 psi but the newer M855 5.56 ammunition is loaded to 58,700 psi. And when the M855 military ammunition came out is when the SAAMI issued the interchangeability warning between the .223 and 5.56.
I have a Savage bolt action .223 with a 1in9 twist that has a longer throat than my AR15 rifles. And I can load this rifle warmer than the .223 loading data for short throated .223 rifles with a 1in1M855 4 or 1in12 twist barrels.
Lake City 5.56 cases are made of harder brass to to ensure extraction in full automatic weapons. And this was just one of the changes that happened after the 1968 Congressional hearings on the M16 rifles jamming problems.
How Hard is Your Brass? 5.56 and .223 Rem Base Hardness Tests « Daily Bulletin
Bottom line the pressures will be higher if you fire military M855 5.56 ammo in a short throated .223 rifle.
The older M193 was loaded to 55,000 psi and the same max pressure as the .223. But the M855 is loaded to 58,700 psi and will cause pressure spikes in short throated .223 rifles.
Below the older M193 5.56 ammunition was loaded to 55,000 psi using American SAAMI standards.
Don't be confused by the military metric designations for NATO ammunition. Its like your speedometer in your car when you are doing 60 mph you are also doing 100 kph but its the same speed.
Not due to the stated load...but unless you have some strain gauges handy, you really can't know where you are with regards to pressure.
And uh. Using range pickup, etc...especially unsorted, IS a recipe for trouble.