Question
Hello. Could a player announce a called shot in the following round he used Prepare Shot [1] to try to get two called shots in one shot? [2]

Example
Round 1: Trotter uses Prepare Shot.
Round 2: Trotter declares 'called shot' before attack. Attack succeeds, he obtains two called shots (and maybe three Piercing Blows if he is lucky enough [3]) in one shot.

References

[1] If the player succeeds in a ranged attack during the following round, he is considered to have successfully achieved a Called shot. (AB p.163)
[2] A fighting character may announce that he is trying a 'called shot' before rolling his attack dice. (AB p.161)
[3] These effects [of called shots] are applied in addition to the normal consequences of a successful attack (Loss of Endurance, Piercing Blow, etc.). (AB p.162)

I've never come across this, but then, I've only run three sessions and my players and I are still learning the ropes as it were. I personally see no reason why the player could not do this, but it would utterly negate the purpose of the prepared shot if they failed to roll a single 6. I'd say they'd be better off just doing the prepared shot and hoping the enemy fails the protection test. There's also the balancing factor. It may seem unfair to melee players that their ranged counterparts can perform such a feat. It also depends on how realistic you want to make it, as the scenario you described would essentially require the character to fire three arrows at once, an impressive act in itself, regardless of whether all three arrows hit the same person. Perhaps implementing a penalty of some form could reflect the difficulty of firing three arrows at once.
Those are just my immediate thoughts anyway

Beleg

That's some magic bullet (arrow).

I think you are assuming that certain things stack, when it isn't clear that they do.

The first is that performing a Called Shot on a Prepared Shot allows for 2 stacked called shots. This isn't the case; an attack is either a Called Shot or it isn't. When preforming a Prepared Shot, trying for a standard Called Shot is redundant.

The second is that Piercing Blows stack. Again, as there is no reference to multiple piercings in one attack, I think it's clear that the rules intend for an attack to be eitehr a singular Piercing Blow or not. Once an attack becomes one from a Called Shot, one generated from the feat die is redundant.

Yes, called shots are applied in addition to the normal consequences of attack, but in the very next sentence they say that the effects aren't always applicable. This would be one of those cases.

Over all of this is common sense. Can a single arrow produce a triple wound that a great axe could never achieve? No.

What you said makes sense to me. And I found this:

In Called Shots table says: "The attack result in a Piercing blow, regardless of the outcome of the Feat die." So, called shot 'replace' (not stack, as you say) a regular try through die roll. The very same idea is present in the sentence: "If succeds in a ranged attack during the following round, he is considered to have successfully achieved a Called shot."

Finally: Prepare Shot -> Successful ranged attack = Successful Called shot = ('Successful' Feat dice) 1 Piercing blow.

Thanks for sharing your ideas, guys.