Oh, you silly boy.

I'm getting a 416 Taylor made up, so, indeed, that will be the perfect short-action cartridge.

There has been some variation in the CZ 550 Magnum Safari boxes and followers and stocks over the years.



I have one that will hold 4 of the Rigby derivative 45 Lapua's (it started off as a .416 Rigby) and one that will only hold 3-1/2 of the .416 Rigby cartridges. The one that holds 4 Rigby sized cases is a little too tight and that first round off the top is a poor feeder. It needs an extra 0.1" of box depth to make it feed smoothly, and thus be a true 5-shooter with 4 down and one in the chamber.



So far in the .375 H&H setup, however, they all seem to be consistent in holding 5-1/2 down, with room for 5 .404 Jeffery's down, due to the slope shouldered and tapered case.



The same rifle that will hold down 5 .404 Jeffery's will only hold down 4 of the .375 RUM or 4 of the .416 Dakota's in the box. That is all that a Dakota 76 African drop box will hold also.



The CZ 550 Magnum is indeed an easy 6-shooter in .404 Jeffery with no alterations, and that is more capacity than the Dakota 76 African will offer.



The .375 RUM took some fiddling to get to feed perfectly, and the factory follower spring did break early on. I replaced it with a Dakota follower and spring said to be for the .416 Dakota, and it worked like a champ. Also, polishing the critical surfaces of the box ribs (stamped into the sheet metal box sides), rails, and ramp, and slightly reshaping the rails in the rear underside helped.



These variations may explain why some of the CZ 550's are smooth feeders and some are not.



The .375 H&H box has ribs. The .416 Rigby box should not have ribs, it is smooth sided, flat sided.



The CZ specs say that the .416 Rigby is supposed to hold only 3 down in the box, last time I looked. Some will hold 4 however. Further study and measurement is needed regarding this earth shaking issue.