How to get P.R.L 412 in Resident Evil 4?

This weapon is one of the rare gun in Re4,people faces enormous difficulties in unblocking/opening this gun.Because of its higher effects and features it is considered to be the one of the best guns in re4 series.So,Lets gonna talk about that how to get this gun,what is the most easiest and quickest way to get this gun.
This trick works on every console..
First it was only on ps2 but later it appeared in PC and Wii.

You can get this gun by ending up the game in professional level,although professional level is difficult enough.So you must end the game in easy mode first and get the two dangerous and infinite weapons named "Rocket Launcher and Chicago Typewriter".
You will face no difficulty while having these two weapons in your briefcase :)
An uncharged shot of this gun will affect in blinding the Zombie for few seconds but can finish the ending monster Saddler.
                          An Charged or fully powered shot of this can kill every monster,doesn't matter how big and how stronger your enemy is..!
This gun can accommodate 3×7 space in your weapon briefcase.It is free of cost and you can buy it from any nearest merchant from zero dollars..!!