doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Needing Low Pressure load for 12 Ga AA

I have a recipe for hunting loads (1 1/8 oz) in a Gold Medal hull. Unique, Federal primer, Fed 12S3 wad. Runs around 7,000 psi, something under 1200 fps. Great pheasant load, works well in vintage guns--although I would not want to shoot a round of sporting clays with it in a 6 1/2# game gun.

It is good to know that because I have been misinformed by barrel makers about this. But 54000 PSI seems to cover 7000 to 8000 pretty well The only barrel fail I have ever had was thought to be caused by an obstruction.

Realize that even though the strength of the steel is given in PSI & the chamber pressure is in PSI, this does not mean that a steel having a 54,000 PSI strength has a 6 3/4 times safety factor for an 8,000 PSI load. The formulas for calculating this are fairly complicated.
For a simplified example a �" steel bar has a bit less than 20% of a square inch in cross section so if made of 54,000 PSI steel it would suspend only less the 20% of that weight without breaking. Dependant upon its actual Yield strength it would stretch long before it broke. In the shotgun barrel a bulge results when the yield strength is exceeded & a burst when the tensile or ultimate Strength is exceeded.
Perhaps one of our Engineers can give us the best formula to use for calculating this.