Couldn't tell from the video what the physical dimensions of the cartridge are, but it would be neat if I could just add a $150 barrel/ magazine to my CZ-455 if curiousity gets the best of me.
In Swampy's link above there is a pic of HMR and WSM side by side. It appears that the WSM may be too big for a standard HMR Magazine ... can't see much regarding head dimensions ... Tried Google-fu, but my skills are weak ... must not be much out there on case dimensions.
