[Unclenick]

CAUTION: The following post includes loading data beyond currently published maximums for this cartridge. USE AT YOUR OWN RISK. Neither the writer, The Firing Line, nor the staff of TFL assume any liability for any damage or injury resulting from use of this information.

.223 started with a 52K CUP MAP from SAAMI. It was revised to 55K PSI MAP by conformal piezo transducer, in one of the more curiously wimpy conversions. I once looked through all the other SAAMI cartridges I could find that started at 52K CUP, and all are now in the range of 60K-65K PSI MAP by transducer. Average is not quite 62K PSI MAP, as I recall. I don't know what went wrong with the .223, but the European CIP has it as 430 MPa (62,366 PSI), and that's worked for them and for NATO so that's the limit I use. If you buy European made ammo, ever, so do you.

As Clark says, many guns can go higher, but throat erosion rates can increase dramatically above the mid-60's, so I elect to stay inside the CIP numbers as best I can.