First off, if you're not running Hemo on this weapon then wtf are you doing? This weapon has forces Impact procs and even with [Lethal Torrent] you're still under that 2.5 fire rate giving every hit a 70% chance to proc Slash, and even without the riven you will be hitting them at least 3 times per shot with a 90% chance of a 4th hit. We want as much base damage as possible to get those bleeds up since this thing only has 10% crit chance. Faction mods double dip on slash damage.

I would love to be able to fit both [Magnum Force] and [Lethal Momentum], but even fully polarized they just won't fit, so I decided on keeping [Lethal Momentum] because this weapon really benefits from the extra range, [Augur Pact] (90%) since it's more damage than a rank 4 Mag Force (75%). You could do a rank 6 Mag Force and a rank 2 Lethal Momentum, but I don't see the point in getting/building a rank 6 [Mag] Force just for one weapon to have an extra 14% damage, and the added perk from [Augur Pact] might come in handy.

If you want more damage then you could trade [Primed Fulmination] off for [Magnum Force] since that would fit, but that is up to you.

If you prefer not using faction mods, then [Magnum Force] over that.

It's really funny getting a much higher KPS in ESO with this than the Nukor despite this being widely considered a useless weapon.

:Non-Riven:
If you're not interested in running a Riven (which is very understandable) then I would run [Frostbite] and [Pistol Pestilence] over the Riven and Auger Pact. You will have plenty of status chance to very consistently proc viral, and it shouldn't reduce your Slash procs since Impact is forced ignoring status chance. The riven with a Panzer is just going the extra mile in optimization. You might also want to switch to Secondary Merciless with this thing's reload time, but it will be a trade-off for less damage.

A lot of my builds are pure slash because the [Panzer Vulpaphyla] is my favorite pet, and it kinda eliminates the need for viral on your weapons. Plus most of them work great even without viral, and then by adding the Panzer you're getting the best of both worlds (two more mods you can put towards bleed damage, and still have the viral procs).