Leupold87 wrote:I have two questions
What is considered over pressured because as I look at some 3 1/2" steel loads in my book with 37 gr of longshot pushing 1 1/2oz of bbs at 1500 fps and has 13400 psi....
And where can I send some shells to get them pressure tested or can I do it myself, because they really pattern great and 1340 fps is great speed for 2 3/4 in shells
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If you are seriously asking that question, I suggest that you not shoot those loads until you have them tested. The MAP (Maximum Average Pressure) for all 12ga shells, EXCEPT
the 12ga 3 1/2 inch is 11,500 psi. For the 3 1/2 inch 12ga the MAP is 14,000psi. For a 20ga, all lengths, MAP is 12,000psi, for 28 it is 12,500psi.
MAP is the Maximum Average Pressure for any SAAMI approved ammunition as measured by piezoelectric transducer 1 inch from the face of the breech. These are AVERAGES, which means that for any given lot, there will be shells that generate more pressure and shells that generate less. SAAMI specifies that your gun is proofed at 170% of the MAP, so for a 3 inch 12ga gun, the proof pressure is 19,550 psi. The guns are subject to special proof loads and then measured and inspected to assure that there is no deformation or yield in the metal work.
So, what does all this mean? For the most part, your gun isn't going to blow up from firing a single load of 12,500psi. Probably not even from a few firings. But, firearms, like pressure vessels, are designed for repeated loadings. Repeated loadings within the design criteria will not present any problems. Repeated loadings above the design loads could lead to a catastrophic failure.
Reloading is not simply a matter of seeing which components will fit into a particular hull. Used to be pretty much that way with black powder, but that was well over 100 years ago. Stick with published recipes until you at least get some more experience with load development. Your fingers, face and eyes will thank you.