Shotshell Pressure Testing Results
 

Sent Federal Top Gun 12 ga. 1oz # 7.5 shot (1180 fps & 1200 fps) and Win Super X paper 10 ga (1 & 5/8 oz # 4 shot) to Tom Armbrust for pressure testing.
The pressures were higher than I had expected.

Usually Tom and Ballistics Products don’t test factory ammo. Nice of Tom to do that for you.
Both of those Federal loads are close to what the factory states. Pressures aren’t bad either.

Hmmm I’ve got a couple boxes of those “vintage” Winchester 10’s . Definitely stouter than I was hoping .

The current maximum average pressure permitted by SAAMI for 12g/2-3/4" loads is 11,500 psi. Anyone buying commercial 12-gauge shotgun ammo that's made for a wide range of guns to include semi-autos should expect them to be loaded to about that max pressure average. CIP (Euro) max average pressure is just a little lower.

Craig, the velocity shown for those 10g/1-5/8 oz/2-7/8" progressive powder loads is comparable with specs when they were introduced.

Thank you for sharing Jim, and I added the numbers here
https://docs.google.com/document/d/1...U/edit?tab=t.0

In a 1927 Western Cartridge Co. flyer “Super-X The Long Range Load” by Capt. Chas. Askins, the Super-X 10g 1 5/8 oz. “about 4 1/2 Drams” (DuPont Oval) No. 2 shot Full choke 32” barrel, average velocity over 40 yds. 1030 fps; “up to 13,000 psi” by crushers = about 14,500 psi by modern transducers.

Some time ago Armbrust ballistic tested some loads from the 30s and found the results to be inconsistent; he felt from primer rather than powder degradation.
It's possible that those shells when fresh might have run higher pressures.