Gardner Deluxe Sausage Gun XT
The same basic internals as the Gardner Deluxe Sausage Gun but with a different cam to provide lower gearing on the compression stroke makes the XT Gun much easier on the wrists - especially with those harder mixes.
A word of caution here; there is a practical limit to how hard a mix can be extruded through a gun, even a tough metal one. If you are having to squeeze the trigger too hard then the mix is too stiff and will be difficult to roll anyway.