Actually, I was curious. I picked up a Lawman Mk III 2" 357 last week; While cleaning and getting better acquainted with it I measured it against my S&W M66 2.5" and then recalled the Magnum Carry, and wondered if there were any difference between the LM3 and the Mag Carry- having never actually had the opportunity to fondle a Magnum Carry in real life.
The Lawman MkIII as expected is quite similar to my King Cobra with regard to the action feel, coil-spring mainspring, bulk, weight, etc. The King Cobra has a few more parts in the sideplate iirc (I took my KC apart once and that will be it!) and Colts in general have more springs inside them than a Smith.
I read that the hammer & trigger of the LM3 were MIM, however mine are case-colored like a nice old S&W, which seems odd since I was under the belief that MIM can't be color-case-hardened.