For 5th Edition, I suggest: a 3 stage weapon (stage 1 fires into stage 2, gets amplified, then fires into stage 3, gets amplified again, then fires out of the barrel).
Acc 9 (scope); DV 15P; AP -10; Mode SA; RC N/A; Ammo: (see note); Avail. 36F (or more); cost 45,000 Nuyen (or more); range (as Sniper Rifle)
A light weight rifle is tethered to a backpack (that contains stages 1 & 2 as well as a satchel power pack holding 20 Power Units). Each shot requires 4 Power Units so the rifle gets 5 shots (but you can plug additional Satchels/ Heavy Power Packs into the backpack for more shots). Note: This rifle MUST be connected to it's backpack with a Weapons-Grade Fiber-Optic cable to function
Otherwise as per the Laser weapon rules in Run & Gun (basics on pg. 47).