That pretty much summed it up, but to go a little further.
A straight-wall case slams into the recoil shield breach-face and expands into the chamber when fired.
But since it is straight, it can still slip back all the way into the chamber when the recoil shield ramp in the revolver pushes it foreword as the cylinder rotates.
A tapered or bottle-neck case slams back, expands, but is then held all the way back by the shoulder or taper. It can't be forced all the way back in the chamber by the recoil shield cam.
So the cylinder won't turn as easy, or won't turn at all.
Carried a step further:
Yes, the old 38-40 & 44-40 rounds had a slight taper or bottle-neck.
But the brass is very thin & operate at very low pressure.
And the SA guns they are normally shot in evolved from the old cap & ball colt design.
Those guns had enough industrial strength cylinder hand, thumb cocked power to grind up cap fragments and spit them out if necessary.
The more modern DA revolvers don't have as much cylinder turning hardware, or mechanical force to overcome such minor things as pushing / resizing an expanded bottle-neck case back in the hole it came out of.
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