Shooting twice is profitable if you go second and heres why:
normal run (both players takes turn doing one shot each, A = enemy, B = you):
1 A
2 B
3 A
4 B
5 A
6 B
3x A, 3x B - fair 50/50 chance
If you go 2nd and do doube shot:
1 A
2 B
3 B
4 A
5 B
6 A
3x A, 3x B - fair 50/50 chance
So far its not profitable, so where does the profit come in?
It's due to human psychology, after having a couple of battles with you and seeing you always shoot twice on your first round they are more likely (not saying guaranteed, however more likely) to start doing the same, and if they shoot twice as first player this will happen:
1 A
2 A
3 B
4 A
5 B
6 A
Suddenly we have reached 4x A and 2x B which means you will win 2 out of every 3 battles where you tricked your opponent to shoot twice.
normal run (both players takes turn doing one shot each, A = enemy, B = you):
1 A
2 B
3 A
4 B
5 A
6 B
3x A, 3x B - fair 50/50 chance
If you go 2nd and do doube shot:
1 A
2 B
3 B
4 A
5 B
6 A
3x A, 3x B - fair 50/50 chance
So far its not profitable, so where does the profit come in?
It's due to human psychology, after having a couple of battles with you and seeing you always shoot twice on your first round they are more likely (not saying guaranteed, however more likely) to start doing the same, and if they shoot twice as first player this will happen:
1 A
2 A
3 B
4 A
5 B
6 A
Suddenly we have reached 4x A and 2x B which means you will win 2 out of every 3 battles where you tricked your opponent to shoot twice.