I see what you mean about the Mannlicher bolt now, I hadn't noticed how far back the image shows it being pulled back.
I'm sure in the physical prop I saw the bolt arm revolved to open the ejection port but didn't slide back much, if at all (maybe the handler just made sure this didn't happen I've watched so many BR pistol you tubes I can't remember which one).
I think any workable compromise would need to feature and explain the mechanics of the prop due to its prevelance.
With that in mind, I'll probably move away from my thoughts as the top barrel having more utility. Instead of being able to fire a wide variety of .223 calibre munitions it is instead purely some form of taser.
The bolt rotates and draws back allowing the cartridge to be hand chambered through the side port. When the mechanism is locked back it crushes the cartridge releasing and compressing the gas propellant ready for discharge.
I don't consider Blade Runners or the Voight-Kampff test to be infallible, it would be useful to have a non-lethal option to hand for those times when they are not certain.
But not a stick thin sonic blaster
The prop's Steyr bolt slides back about one centimetre — nowhere near as far back as the drawing shows.
Again, for my own part ... I don't really see elaborate non-lethal functions being a priority for police sidearms in such a Noir world as Bladerunner's. The only concession to reducing collateral damage would be not having every round be explosive, but only those specifically activated to be.