I was out in the shop yesterday and spotted some .378 WTBY brass in a box and decided to chuck a couple of them in the lathe and turn the belts off to make up some dummy rounds to play with. For simplicity, I left them .375 but the idea is to use them to see what needs to be done to open a standard Mauser to work as a 416 Rigby. I have a Mark X that I had already opened fore and aft for a Lott and, outside of opening the front of the rails a bit for release, it looks fairly straightforward. If you use the Mark X T/G, it looks like either you need to convert it to inline feed with only a two round capacity, or go to custom bottom metal. I remember seeing articles on a famous PH's original Rigby(his name escapes me) That was on a standard, but I never saw any mention of how the bottom metal was reworked. I was looking on Cabelas and they have a .378 WTBY on a Mark X but no mention of capacity and I am curious if anyone can tell me what is usually done. Thanks, Lee.

The famous PH was Harry Manners or Selby??? His rifle was built by Rigby and as I recall, he bought it in Africa. Rigby obviously would be a place to inquire. especially since they are primarily based in Paso Robles, CA. Actually, although most people will advise against this, I would check with PreciseMetalsmithing, D'Arcy Echols, Ted Blackburn, or Tom Burgess if you are bound & determined to do it.

I can't tell you specifically how it is done, other than opening at the front & rear, but I did see a Mark X in 416Rigby at a Houston gun show a couple years ago and I've seen pics of Harry Selby's Rigby, so it can be done on a standard length.

Opening the action at the front and rear is pretty much standard, the Rigby is only slightly longer than the 375 H&H. I can handle that. I also saw the MK X that you saw at the Houston show, but the seller was tied up with a customer and I was in a hurry, I wish I could have gotten a closer look at the bottom metal. Dropping the dummies into a MK X box, there is almost no stagger, so it looks like to use it, you would have to fabricate some feed lips to the stock box and make it a single stack. Thats why I was curious about how they did it pre-war and if it was custom metal with a wider box. I was guessing that if they built it on a standard Mauser, they might have adapted the standard mag too. I figured with all the experience on this board, someone had done it!

Let me invite you to come shoot my 416ar or my 550 express (which is a belt "rigby" in the form of a weatherby case, shortened)... then you can understand what a super long single stock would look like, and what you would have to do to build a stock.

the 416 AR matches the rigby factory loads, easily.

feeding will be as NIGHTMARE in a stagger mag...

seriously, a nightmare.

that it is only "slightly" longer is like being slightly pregnant.. the 375HH length (3.65) is .300 LONGER than a 30-06 ...

that it seems doable is actually a voice of a wood worker, not a metal worker... .400 (the additional rigby length) and .585 diameter rounds (bv .532) means the box and rails HAVE to be .100 wider than an HH based round.

if I could be talked into it (NO BILLY), it would have to be single stack... as you mention..

and, without a major stock rework, would hold TWO down...

IIRC (and my memory isn't what it used to be) there was a article about making the Rigby work in a standard magazine. Anyway I seem to remember that to get it the proper geometery it required using the stock wood itself for the sidewall of the magazine.
I don't remember if it was a 98 or a MK-X action that was used, but if you tape a 5-pack of brass together in a staggered (3-2) configuration you will get a real good idea of how wide the box needs to be.

I thought I had more pics of Selby's 416. This is the only one I can find at the moment;

You could use a .416 Remington.

I already have a .416 Rem, I am interested in doing a Rigby myself just because I would like to do it. I was inspired by Selby's rifle and just like the idea of one on a standard size action. I was, however, looking at my Lott on a pre-64 M-70 and it looks like it would be a bit easier! Bottom metal seems to be the bugaboo right now, I will call Blackburn Machine and see what they say. Jeff, thanks for the invite, I am always up for shooting big bores! Lee.