*This video is for people who want to play it safely.
Please read the description for valuable hints.*
This pistol is a reward that ONLY unlocks if you completed 26 (TWENTY-SIX!) escalations on Locations: Hawke's Bay, Miami, Santa Fortuna, Mumbai, Whittleton Creek, Isle of Sgàil, New York and Haven Island.
in short:
(first you need to play "Three-Headed Serpent" in Santa Fortuna, the escalation unlocks alongside the mission)
You need to get Silent Assassin ONLY on this third level
WAIT until you see the on-screen message "unnoticed kill" for the last target BEFORE you exit the level or it may not count towards unlocking the gun EVEN if the rating is Silent Assassin
This video should make it easy for you to get your SILENT ASSASSIN rating for level 3 (you NEED that rating) and by that, to unlock this nice pistol.
Also, you'll manage the first two levels (no Silent Assassin needed for level 1 and 2) of this escalation, too, by watching this video because it's essentially the same, only less stuff to do and therefore easier ;)
Don't forget to get the speed boat key, see 6:50 which was perhaps a bit quick to realise what I did.
You need to get Silent Assassin on this third level of The Delgado Larceny escalation in order to unlock the gun which is why I didn't play it like on steroids. To me it's about playing it as safely as possible, not getting caught and not having to worry about those 80 seconds by wasting time luring the target or getting caught in the process.
However.. I made a funny and silly little mistake by not picking up Bañuelos's gun, actually I didn't expect anyone to find it. I was happy that I found a safe way to hide after the loud shot (guards are damn fast getting there and spotting you.. so hide in the tunnel to avoid that) and then.. edit: I should have either picked up the gun on my way to the tunnel or should have continued to run towards the helicopter. I really didn't expect the guard who picked it up to take it JUST towards my nice hiding location and I was getting slightly nervous there. Don't do that, don't forget to pick it up, saves you both time and nerves. :)
What tends to go wrong is luring the second guard into the room at the start. It may happen only IF you take out that second guard without dropping a pistol in front of the radio (I found that out later) For some reason he tends to see your unconscious target on the ground around the door but if you drop (or leave) the gun from the first guy on the floor in front of the radio, he instantly sees it and goes to investigate. That is better than just the music and he'll likely ignore the rest once he's focussed on that pistol. But you won't lose much time restarting if it goes wrong. I took him out because he's an enforcer and potentially screws up your attempt.
The rest is absolutely fool-proof :) By the way, just to be safe, I tucked away the explosive, away from the wall where the safe is, because depending on your timing, sometimes people are right on the other side of the bathroom wall and I didn't want to blow them up through the wall by pure chance.
Want to add a new gun to your collection? Missed out on the Striker Magnum pistol because it's a legacy Hokkaido escalation? Well, it's the same gun (stats) with even nicer looks. :)
Good luck and thank you for watching my video :)