As is, you can stuff four rounds tightly into the box, but the bolt scrapes over the top round when closed, if it will close, and the tight top round will not feed off the top, it's a jam.

Drop the floor plate by 0.100" with pillars that extend downward that extra amount, 0.100" or less, and the magazine box will hold and feed well 4 rounds from the box. A five-shooter .416 Rigby CZ 550 Magnum. Comments?

Doesn't a 550 CZ hold 6 rounds of 458 Lott?

You could always buy a Hyem Express rifle it will hold 4 rounds in 416 Rigby.

Thanks for the advice I was wondering about how to do it. Is this something you have done or just trying to work it out?

Thanks for the tip Daga,

I love to read anything about cz's

Replace the floorplate with a Rigby Pocket plate.

The 416 plate is deeper to hold the 4th round, You also can put on the 375 action and gain one more round.

I have the pocket plate CADed and rough programed. Just have not had time to make chips.

Been busy pouring concrete on my addtions.

Check back in another month or two. I have to also make two new fixtures to hold them on second operations.

James Wisner

Jim,
I'm going to want some of those when you start production...

A dropped floorplate is the proper way to go! Given how the CZ action works simply adding pillars will cause a gap that will allow the mag box itself to drop out of its engagement with the action. The resultant gap will cause failures to feed properly. Particularily with soft points. You should fabricate a new mag box at the same time for this to work. Sounds good at first but it isn't good gunsmithing. In any event the floorplate will no longer sit flush with the stock and will look amateruish.-Rob

Mr. Wisner,
Thanks for the comment. I will want some of those too. I have several of your Pre-64 African express sight reproductions, on rfles, and one of your three position safeties. Excellent stuff.

Rob,
I am waiting on the Wisner floorplates. Until then my method is not all madness. Actually that sheet metal box in the CZ can be made to stay engaged. The recess that the box fits up into, at the magazine port of the action, has walls that are close to 0.200" deep. So if the box is dropped only 0.100", it still has 0.100" gripping it, and is not bottomed out, and going nowhere in the rifle. No misfeed problem. A similar 0.200" retaining recess in the floorplate grips the box at the bottom, and there is no way the box can tilt or get loose. It just hangs there, only 0.050" of top and bottom of the box are freed up, and it is still walled in, just floating, not bottomed out, securely gripped and stable in the pillar bedded action. It ain't goin' nowhere!

Those who want to experiment with this can just add 0.100" thickness of washers on the action screws, fore and aft, but pillars will prevent compression of the stock and keep the distance fixed.

As for the small protrusion from flush of the floorplate: Not all of us are so prissy about our rifles. Remember Finn Aagaard and his epoxied crossbolts on his old Winchester? A working gun can have a pimple or two.

Until I can do better, it will do just fine, and is flawless in function as is.

Coondawg,
I have done it. Just sharing, and looking for comments such as yours and others'. Thanks. It works just fine. You end up with just 0.05" extra space on top and bottom of the box. Fabricating a new sheetmetal box would eliminate the tiny gap, though the Wisner pocket plate and appropriate box would be very nice, eh?

Dragon Red it sounds real easy but how easy is it for someone to do that is not gunsmith capable? The box sounds almost like a drop in but I know better than that.

If you were just starting out which way would you go? The reason I'm asking I going to build one of Judsons .366 D.G.W.s on a CZ550 SMs and would like to have that extra round, just because you never know whats going to happen.

How deep does a plate have to be to be a pocket plate? What do you call a plate that is deeper than a pocket plate? A BIG pocket plate? Just curious.
Here is one that is definitely going to be able to hold another round. O.750".

Nitroman that round looks big enough to take down a BUFF (B-52, buff that is) What is it and that box for a mag?

Just a quick question. The Montana magnum action, not the PH version, how many rounds will it hold of say .375 H&H? Is there a drop box available that would fit that action?
The reason I ask is that I'm left-handed and have ordered one of those actions.

Coondawg,

That is a .600 Rothschild, Rimless Belted Nitro Express, 3 inch version. It will be going into a P-14 Enfield receiver. The magazine box is welded to the receiver rails and can hold two cartridges easily. To make a third fit comfortably, I needed another 0.675" or so. A very generous gentleman out of Trinidad, Colorado who is in a machinist program at a local community college did the machining for me. That is 4140 steel.

The new plate needed a longer but slimmer triggerguard frame so I made that (in the background). The frame will be welded to the old Enfield triggerloop so the whole assembly will be the same length as the original.

I have much work cut out for me. I need to measure and scribe lines, file (LOTS) and fit the plate to the new frame then I can send it off to my 'smith. While it does look like metal brick right now, by the time I am done with it most of that steel will be gone and pleasingly rounded corners will be left.