Why use short cases in a longer chamber?
Well, sometimes it's all that there is in quantity. Like 35 years ago when I got this damn rifle. When I got an ever-increasing supply of, even then, old Western cases of the full length they shot no better. Kept using the mix without worry for all this time.
And, if my accounting is correct, for a quite few thousand shots- with the rifle improving in small increments with time. Probably brought on by the theory that even us blind chickens find corn. 
I agree with you that the .32-40 is still a viable choice- even in the age of the more recent, and successful rounds. 
John, nobody is being argumentative here. Yet..but I'm getting sore at having you "determine" that we are. 
Jubilado, I think you have a lot of good choices for your barrel's chamber. None truly poor ones. A hundred thirty-odd years of the old Ballard round sure is a good recommendation for it. I rest my case on its record. 

Ken, I'll butt in here to tell you that I admire your setup. It's a bit advanced over mine. But, it's become comfortable for me to use, and we all know how that works. 
With the results you get, don't be surprised to see a lot more of them like yours show up.

Mine vary depending on whether they are necked up .30-30 or from pushing the shoulders off of .32 Spl. The shorter ones run about 2.05 to almost 2.09. Compared to the trim length of 2.12 for  the .32-40 case it isn't a large amount. Plus, they never need trimming for any reason beyond squaring mouths.
The most recent cases made may be a little shorter- like most factory brass seems to be these days. I just got some .280 Remington that is almost as short as .30-06. May be made from the same stuff, just finished a different way. Cost cutting at it's silliest. No harm, just silly.

PM sent.

Paul