DUGABOY - I think you are giving 416 Rigby pressures a bum rap. Original Kynoch loads listed pressures, as you correctly stated at 17 tons per square inch (tpsi)-actually up to 18 tpsi for the 410gn load, which is not out of line with many flanged cartridges widely used for double rifles such as 450NE - 17 tpsi, 450/400NE (3 & 31/4 inch)-16-16.5 tpsi, 500NE - 16 tpsi. 375 Fl. Magnum at 18 tpsi equals it, and that probably explains why some rifles of inferior design and make do shoot loose! Not forgetting the good old "low pressure" 303 British at 17.5 - 18.5 tpsi, depending on load. Further, when Graeme Wright took a range of handloads to the Birmingham Proof House, mostly based on proven IMR 4350/4381 charges, the pressures were invariably down on the original Cordite loads. and, by the way - you can't simply multiply old copper crusher tpsi x 2240 and get psi in modern CIP or SAAMI equivalents - dangerous notion the needs to be laid to rest. I don't know what load Federal use for 416 Rigby, but presumably, with modern powders, they should be similarly down on the Cordite loads. But - handloading? Well, if some dickhead wants to experiment with hot loads in doubles - then that is only the evolutionary process of natural selection at work. For me it is comforting to know that he wouldn't be doing it with an original Rigby - since, as I say - they didn't make many 416's. In other words, if he blows himself up, and some other shitbox brand of rifle up - then it could only be a good outcome all round!