The current SAAMI maximum pressure for a 16ga 2 3/4" cartridge is 11,500psi regardless of shot and powder loading. At 80 percent of proof pressure, this requires minimum SAAMI compliant proof of 15,365 psi for a 16 ga gun, manufacturers may exceed the minimum standard .
Current production cartridges may be at or below the 11,500 pressure, particularly 1 1/8 loads.
At the time the Parker in question was made, the normal max pressure for 16 cartridge was 10,200 if I recall correctly, this gives a minimum proof load of 12,700 that the gun would have been tested with.
Tests have shown that chambers 1/4 " short increase pressure over nominal 2 3/4 by about 5 percent. Therefore assuming it was short by 1/4 " ( which may or may not be true) , a possible pressure could have been 11,500 plus 575, 12,075.
Therefore, the maximum pressure that factory shells loaded to maximum SAAMI specifications would have provided exceeds the load pressures the gun was intended for but remains less than what the gun was proofed with. The few tests done and reported in DGJ have demonstrated that the tested composite steel barreled guns withstood at least 4000 to 5000 psi above proof before they experienced non elastic deformation.
Neither the bore ID nor wall thickness has been disclosed for the gun in question. That information is critical to any informed analysis. O framed 16's , which this may or may not be , often do not have much wall thickness to spare.
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