Triple tap/vorpal/extended is the important part, for the rest YMMV. Mine has a handling masterwork w/ fluted barrel, handling upgrades are always nice for snipers.

What I'm not totally sure about is Boss Spec versus Backup Mag in terms of mods. Boss Spec gets you more damage per shot, but Backup Mag gets you a theoretical 7 shots without reloading compared to 5 without. Probably worth testing, it may be a DPS vs. total damage thing.

Ah, I hadn't really thought that through. Using Boss Spec only adds 7.8% damage per shot - that's not nearly enough to compensate for the triple tap change. (With 5 shots, hitting all crits, you get 7 shots with Triple Tap before reload. With 7 shots, you get 10 shots before reload.)

What I'm not totally sure about is Boss Spec versus Backup Mag in terms of mods. Boss Spec gets you more damage per shot, but Backup Mag gets you a theoretical 7 shots without reloading compared to 5 without. Probably worth testing, it may be a DPS vs. total damage thing.

Now what this gets you is the ability to keep up with Whisper without using your exotic/heavy slot. For the current raid, I like to run Huckleberry/Trophy/Linear Fusion on the third encounter, and Huckleberry/Trophy/21 Delirium on the fourth, loadouts which give both DPS and super fast ad clear. You can get something similar with Izanagi's/Recluse, but I find the Izanagi reload tuming and the added pressure of hitting crits to be unpleasant.

(That's Fullbore/Extended Mag selected, Corkscrew Rifling/Steady Rounds not, if you need them)