Howdy Again
I was referring to attempting to fire a 44 Special in a 44-40 chamber, not a 44 Mag. As it turns out, you cannot chamber either in a 44-40 chamber. Just tried. The 44 Special won't seat by about 1/8", the 44 Mag by almost 1/4".
The reason is the thickness of the 44 Special brass, or the thinness of the 44-40 brass, which ever way you want to look at it. Even though they are close in bullet diameter, .427 for 44-40 and .429 for 44 Sp, the thicker brass of the 44 Sp brings the case diameter to .4565. The thinner brass of the 44-40 means the case diameter at the mouth is only .443.