I don't think that you will know this one (excepted the Europeans)...
I have tried to scratch built a blaster in resin, from the "Ulysses 31" anime ....
But I have two left hands... I have done the prototype in wood/PVC tube... But the molding result was awful, even if it was my first try to cast/mold.... It looked like a sextoy loooool !!!!
:lol
It looks like the Mateba Model 6 Unica. I've seen one of those in a live-action movie called, Give 'Em Hell, Malone.
For me, I picked up a B.B. Gun that looks like a .357 Magnum, with the intentions of possibly turning it into Taki's gun from the 1987 animated film Wicked City (trailer). I've read the book, to which the gun is a normal .357 that, with the psyonic power that a member of the Black Guard by channeling the psy power into the bullets so that it can be useful to destroy Black Worlders. In the anime, they changed it to give an explanation that the gun was modified and that the ammo packs one hell of a punch, no matter who's holding it (there are multiple times where you see Taki firing one shot and getting propelled back).
The problem with the B.B. Gun, a Crosman I picked up (pictured here), not only is missing one side of the grip, but its a break-top design. The gun in the anime is a normal side loader (meaning that the rotating cylinder comes out at the side to allow for the empty rounds to be ejected and fresh rounds to be loaded.