I read a article over at Authentic Campaigner website (highly recommend for any ACW reenact ors,
http://www.authentic-campaigner.com )
They had a article of how to die by using report of wounded soldier's comment of their experience of being hit.
Now, Not every bullet kills, there were a thing called spent bullet. Basically, not enough of gunpowder so upon being hit by a spent bullet, you will be knocked off few feet behind then shake it off and carry on forward. There are events where a bullet will hit a nerve, causing spastic movement upon death.
Heres what I do sometime, depending on scenario itself, if its 1861, that would be where I would a fresh fish in the war. A volunteer seeking for adventure, I would spent my time ducking and constantly looking around then bam hit, i either take a flop or panic where I as I ran away from a battle. Yes, I ran at a Bull Run scenario. But if its mid-year, where I've done some battle (historical speaking). Ill either get hit and slowly fight on forward as I am bleeding then fall.
There are actually some situation where there would be small agreement between pards about taking a shell.
We actually did it once and a shell took down 4 guys including me quickly falling back to the ground.