As Intel6 noted, converting a .40 S&W 1911, like a Springfield or Kimber, is not too difficult, and the "conversion" can be set up to work reliably and, apparently, for a reasonable co$t. Pistolsmith Dane Burns offers such a package on Kimber .40s. Mags that feed reliably with both the .40 & 10mm are readily available too.
For non1911 pistols the real problem, IMO, is mags of the correct size for 10mm, even assuming your .40 pistol could be properly sprung & buffered to reduce pounding from much higher slide-velocities against the typically 9mm-sized frame.
The Glock 20 was purpose-built from the ground up to handle long-term abuse from hot Norma-strength 10mm, after which it's counterpart, the G-21 in .45acp, was then created. Most polymer .40s (e.g., P-99) would lack the same designed-in durability for this higher power round.
Still, the idea of a "10mm conversion" makes for interesting speculation, especially if you have a real love for this cartridge.
Not too long ago, I examined an all-steel CZ 75B in .40 S&W (beautiful pistols, btw) with a gunsmith/dealer friend. We took it apart for this very reason, just to see, theoretically, what work would be needed for a "10mm CZ conversion."
We already knew there would be a mag-size issue, but we wanted to look a little further anyway, because the other dimensional considerations appeared correct - other than needing to ream out the barrel, I mean.
On closer inspection, while the .40 CZ 75B is somewhat beefer than its 9mm counterpart, my 'smith bud felt the strength level just wouldn't be there, given the penchant of a 10mm shooter (like me) for the hotter loadings. He felt it could probably sustain abuse successfully from "several thousand" .40/10mm 180gn rounds "loaded to no more than 1000fps" (his prediction). In other words, even if you got by the mag problem, you could only shoot 10mm ammo loaded no hotter than the hottest .40 loads using 180 gn bullets. So, for the co$t involved, why not just stick with the .40?
OTOH, we also looked over a CZ 97B in .45 acp that he had for sale at his shop. While there are too many issues to overcome for a "10mm conversion" on the 97 directly, there's no question that the gun itself is OVERengineered for the 45acp. With a different slide, barrel, breech-face, extractor, springs, etc., the CZ 97 could be set-up to handle the 10mm (again, assuming access to specifically dedicated 10mm mags, like the Tanfaglio Witness uses).
Whether the CZ people could be convinced that there's enough of a market here for a CZ 97B in 10mm to justify the cost of production is a different question. Until then, "conversion" is just a theory.
