I remember when this thread was active, and when I just reread it a thought came to mind that was not directly addressed. There are a number of 2.5” originally chambered guns that have had the chambers lengthened and reproofed in England. My thought is just because they have been reproofed for the longer chambers should modern 2.75” ammo be used? If pressure is the primary factor, are shooters mistaken in the notion that 2.75” chambers can accommodate modern ammo? Seems like if a gun was originally proofed at 2.5” with the associated pressures of that shell nothing has been done for the sake of safety, particularly when metal has been removed from in front of the chambers. I’m convinced low pressure in 2.75” shells is probably better than removing barrel wall even if the gun is reproofed. If the gun has had the chambers lengthened and been reproofed lower pressure ammo should still be used.