doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com pressure rating for 1220 12 ga ammo

Federal and Herters each sell 3-1/4x1-1/4x 1220fps shotshells an old standby. What is the psi rating for these?

Below SAAMI max.

Best,
Ted

The only way to know is to send samples for pressure testing and pay the toll. And, after you get the results you will only know what the pressure was for that particular lot. Next lot may, or may not, be different.

As said, only the makers know, and they aren't sharing
I've never seen independent testing for the 1 1/4 3 1/4 loads

For a historical perspective, from “Smokeless Shotgun Powders: Their Development, Composition and Ballistic Characteristics” by Wallace H Coxe; E.I. du Pont de Nemours & Co., 1933, for a 3 Dr. Eq. 1 1/4 oz. load.
Pressure by modern piezo transducers would be 10-14% higher.
DuPont Bulk = 9,600 psi
FFFg = 9,000 psi
DuPont Oval = 8,700 psi
DuPont MX = 9,800 psi
DuPont MX Smokeless was a Dense Multi Base Powder introduced about 1928. 25.5 grains was 3 Dram Eq. and it was promoted as a 1 1/4 oz. Trap load. It was replaced in the 1954 with IMR PB.

IMHO it is safe to assume a modern 3 1/4 Dr.Eq. load pressure would NOT be any less.

A Winchester Reloading Manual (I don't know the date or if the pressures were crushers or piezo) listed that load with WSF at 9000 psi
https://www.appuntidiricarica.com/pluginAppObj_120_24/Winchester-Reloaders-Manual-.pdf