Thel said:
The 10mm GP uses a barrel with a thicker shank
I was curious about this so I went and took some measurements.
The 10mm GP uses a 2-piece barrel; the forcing cone end of the liner is hex-shaped and appears to tighten into a counterbore. I posit this change was made for manufacturing reasons that have nothing to do with the strength of the forcing cone area.
Examples I have access to:
.357 GP has a FC OD of ~.5126"
10mm GP has a FC OD of ~.6308" to the "points" of the hex (unfortunately, forgot to measure the flats)
.44 GP has a FC OD of ~.5144"
For comparison:
.41 Redhawk has a FC OD of ~.6720"
.44 Redhawk has a FC OD of ~.6805"
Measurements from a S&W N frame or a Blackhawk would probably be more comparable given the barrel shank size is close to that of a GP. Makes me wonder about the S&W 69, since the L frame shank size is smaller than a GP (at least for the pre 2-piece barrels).
TL;DR: I doubt there's enough meat in the GP forcing cone/frame area for Ruger to attempt a .44M model. .41M certainly seems doable but given the lack of commercial ammunition, probably not profitable for anything other than a distributor run.