I'll go out on a limb and say, YES, it could be a practical substitution if one really NEEDED to do such a thing.

I have both a Ruger .416 Rigby and a C&H .404, and a goodly supply of X Bullets for both. I just tried a .416-400 X-bullet in the muzzle of the .404, and it is a LONG way from a "rattling" fit. A fair part of the ogive is still outside the muzzle, even with a hard thumb-pressure push.

The big problem in loading .416 bullets for use in the .404 will lie in getting a sufficiently-secure bullet fit in the case neck. By neck-sizing the .404 case in the Rigby die, it SHOULD retain the bullets well enough, but you have got me thinking now, so I'll give it a try in the morning.

Since I have identical-weight X Bullets in both diameters, .416" and .423", I believe I might's well see what happens when I fire a few of them side-by-each over the chronograph. I'd hazard an opinion that there won't be much velocity difference OR accuracy difference between the diameters. Might take a few days, but as I say, I'm curious now...

There's no real reason for such a substitution in most cases, but if you're living miles out in the outback and suddenly find you're out of .423s and still have a few .416s.....???? I lived for a LONG time (decades) in such a location, and can well understand just why such a technique might be needed.

Incidentally, I have already successfully fired RCBS 416-350 cast bullets through the .404 with decent accuracy. These bullets measure .4165" and grouped rather well.

Roger,

Your friend might slug the bore of his .404. I have seen results as tight as .418" reported by owners of older rifles.

jim

BruceB,

Ya. it's amazing what a few WILD TURKEYS will do to your thought process. I hate those damn birds!

Roger QSL