Your note on magazine box geometry prompted me to measure the mag box Gene Simillion built and installed on my M-70 Classic when he built the 460 G&A. That cartridge is based on the 404 Jeffery case, the example you provided. The mag box is wider and completely enclosed on its sides, front and back; there are no windows.
Interestingly, though it fits flush with the belly of the M-70 factory wood stock, it fits 4 460 G&A cartridges. The stock recess for the box has been slightly enlarged laterally internally, though almost imperceptibly. As a test I also confirmed that the box accommodates 5 belted magnum cartridges. This magazine also uses a custom made follower which has a subtly formed shallow groove which causes the left sided cartridges to straighten into the middle of the feed ramp as they feed. Interesting idea which makes for extremely smooth and reliable feeding.
Seems there are several interesting ways to skin the increased mag capacity cat. I like the flush fit because it preserves the lines of the stock. However, that’s a purely aesthetic personal consideration.
Is life so dear, or peace so sweet, as to be purchased at the price of chains and slavery? Forbid it Almighty God! I know not what course others may take, but as for me, give me liberty of give me death! P. Henry
