Formed the first 5 460 G&A cases easily today in the CH4D sizing die with one pass using 404 Jeffery basic cases. Set headspace on these cases to the dimension of the Mason go gauge. The formed cases required trimming of almost almost 0.15” of the neck to achieve the max COL of 2.800”. They’ll serve as the basis for dummy rounds for the GS building the rifle to ensure 100% function as a DGR.
Moving the shoulder forward and decreasing the taper, compared to the parent 404 J case, was obviously a very good idea. Given that the 500 grain 0.458” monolithic solids are longer than the 400 grain 0.423” bullets, the taper change and relocating the shoulder forward prevent loss of powder capacity. Although I’ve not measured the capacity I anticipate that these changes may have increased the capacity slightly. It’s also obvious that the 3.6” COAL, which allows building this cartridge in a standard Win M-70 length action does not maximize the newly gained powder capacity.
Because I have a 450 Rigby DGR I’m having an opportunity to compare it to the 460 G&A with respect to design of the 2 cartridges. If the 460 G&A were built on a true magnum length action, such as the Ruger RSM or one of the magnum Mausers, a COAL of 3.720” could be achieved. Loading a 500 grain monolithic bullet (Barnes, CEB BBW #13) would preserve the entire powder capacity of the 460 case, with the base of these bullets flush with the neck-shoulder junction. Of course, the whole rationale of the G&A cartridge is to provide similar performance to the 450 Rigby or Dakota with less powder, albeit at a higher chamber pressure, while allowing building it in any action that allows 3.6” COAL (ie, 375H&H length) cartridges. Slighter shorter bolt throw (probably insignificant functionally) but greater selection of actions (much more important).
I’ve been documenting the process so far and will post the pics at some point, once the rifle is ready and load development is underway.
