OK, here goes, though I'm thinking it might not be the best example as it seems pretty much just a magnum revolver as I recall. Maybe I'll tech and butch it up a bit to make a better example
This is for Classic Traveller Book 1 - Characters and Combat (aka LBB1 for Little Black Books 1):
Looking at the available weapons we have a (Magnum) Revolver to build from. Our goal is a marginally more powerful handgun with a revolver action and reduced load (5 shots) and some presumed higher tech level modifications (those blinky lights and double trigger must do something right?).
LBB1 Revolver: TL4; 0.9kg unloaded, Cr150 (6 rounds 0.1kg, Cr5); 3D damage; Dex 9+ = DM +1 or Dex 6- = DM -2
Armor: Nothing +1; Jack +1; Mesh -1; Cloth -3; Reflec +1; Ablat -1; Combat -5
Range: Close +1; Short +2; Medium -3; Long -5
We can't add to that too much and stay realistic and true to the movie. What can we tweak?
Let's start with damage. Increasing the lethality at the expense of fewer rounds in the gun. Bigger bullets, basically. A full dice of extra damage is too much though, and in "fairness" 1 bullet less averages about 11 points of damage, divided by 5 bullets, gives about 2 points per bullet. So our new damage rating is going to be 3D+2. Sounds good to me.
Let's tech up the materials and make it a little lighter. Say about 20% lighter in round numbers... 0.7kg for the weapon and keep the 0.1kg for the 5 bullets.
Cost is going to go up for the advancements (we'll get to those) and materials. How about half again as much... Cr225 for the weapon. I like the Cr5 for 5 rounds but these bullets turned out (see below) to be something special, so I'm going to double that to Cr2 per bullet.
Those two triggers bug me. I don't recall them doing anything in the book or movie but it's been a while since I've looked at either. How about 1st trigger is standard, 1 pull 1 shot. While the 2nd trigger is a burst fire mode, powered by a limited use battery, 1 pull fires all 5 bullets to give the standard autofire benefits?
How about some tech? It's kind of neat that (as I recall anyway) Deckard isn't reluctant to fire on a crowded street. He must be pretty confident those power loads won't overpenetrate and take out innocents or damage property. Or he just doesn't care
Yeah, let's go with some tech that does that and flatten out the range modifiers for a twist. How about:
Range: Close +2; Short +2; Medium +2; Long NO
So we have a gun that is smart about not shooting at range beyond what is relatively sure of hitting and tailored to deliver the same lethality at all ranges.
I think that looks pretty good. In summary and format:
Model 2019 Detective Special: TL9; 0.7kg unloaded, Cr225 (5 rounds 0.1kg, Cr10); 3D+2 damage; Dex 9+ = DM +1 or Dex 6- = DM -2
Armor: Nothing +1; Jack +1; Mesh -1; Cloth -3; Reflec +1; Ablat -1; Combat -5
Range: Close +2; Short +2; Medium +2; Long NO
Autofire Bonus: Pulling the second trigger when fully loaded (5 bullets) engages a powered action (drains the battery) that fires all the bullets very rapidly. Use the full automatic fire rules. A Model 2019 with a dead battery is limited to single shots and defaults to:
Range: Close -2; Short +0; Medium +2; Long NO
Care must be taken as the weapon is prone to over-penetrate at closer range without the benefit of smart ranging.
...of course there are as many ways to do this as there are refs and players
Caution must be exercised to not go too far though (I hope I haven't). In a 2D6 system every point counts and a full die counts for a lot.