You piqued my curiosity about using the WSSM case. I like the 416 cal, have a 416 Taylor and was considering building a rifle using one of my extra SA Rem actions and the already developed 416 WSM.
I ran some numbers through WinLoad and Load Disk for a 416 WSSM using the Barnes 350 XFB, it having a very high BC...the Barnes 400 gr XFB having the highest. I came up with 1700-1950 fs at a max of 52 KCUP with both programs, using H4227, AA2015, or RX7 in a 20" bbl. Of course, actual load testing could produce different ballistics.
Empty case capacity is about 52g H2O at 1.67" and about 40g H2O with the Barnes bullet seated to 2.6" COL...I'm not sure what the magazine max cartridge length is in the rifles you're talking about.
I didn't even consider the WSSM case when I was looking at using the WSM case. Now that I have and even though it is an interesting concept, I would not consider actually building a rifle using this case. To my thinking it would be a lot of work for not much result in comparison with the larger WSM case, but I would be very interested in following post from someone who is actually building a rifle. The ballistic numbers would equal a standard 45-70 with equal bullet weights tho', in a much smaller package, so it isn't really a lot of work in that respect.
I also looked at the 44, 45 and 50 cals using the WSM case (all could be done to the WSSM also). I know of at least one 458 WSM, and one or two blurbs using the 44 cal, but nothing larger. A 50 cal would be a straight walled case basically and there are just a whole bunch of other good 50 cals, rimmed and rimless, out there already available, so I put that idea aside. A 375 WSM has also been done and the same caliber using the WSSM case would be an excellent prospect also. It might even be ballistically superior to the 416 cal using a 350 gr Woodleigh.
At one time there was a site dedicated to the WSM and WSSM cases but it went by the wayside...and I sure miss it.
The 458 is eminently do-able and produces some very good ballistics, but other things got in the way at that time and I didn't pursue the matter...plus I still like the 416 WSM concept and will probably do one someday. I'm just finishing up my 460 Boondoggle McWildman so the need to breed is already working at my loins, so to speak, to get started on another project soon. I seem to be building more large caliber boomers the last couple of years than anything else.
As far as necking up is concerned some used Redding expander buttons and some just fireformed, or a combination of the two. In the bad old days some would use a stub barrel chambered for the case or make a "gun" that screwed onto the sizing die to firefore...haven't seen one of those in 40 odd years...not since the hayday of wildcatting.
I think going where no one has gone before is the heart and soul of 'Catting...doesn't matter the reasons pro or con.
Good luck if you decide to do this project.
