[Rauta] provides 2 melee combo per pellet and caps out at 28 per shot. As such, a multishot of 14 and higher is needed to maximize combo gain per shot.
4 rounds will provide 96 combo and 8 rounds will provide 224 combo; enough to hit 12x for a regular melee weapon. For [Venka Prime], 9 rounds will be needed to hit its max combo for 13x.
Max Fire Rate is 0.8, so fire rate mods are essential. It should be noted that the trigger type is semi, so excessive quantities of fire rate will be difficult to fully utilize comfortably.
Reload is fairly quick at 1.2 seconds.

The weapon is not designed to deal damage and is best served for quickly building melee combo. It is best utilized for melee centered builds and playstyles, especially for Warframes with exalted weapons like [Khora], [Baruuk], [Excalibur], etc.

This build does not cost any resources whatsoever, excluding the time necessary for the weapon to have a mod capacity of 30.

R3 [Hell's Chamber] is utilized to hit the desired multishot target of 14 without wasting additional mod capacity.
R5 [Shotgun Barrage] and R4 [Frail Momentum] are used to consume the remaining mod capacity and increase the rather low fire rate.
R4 [Shotgun Barrage] and R5 [Frail Momentum] will also yield the same results if you do not have additional copies of the Corrupted Mod.

The weapon has rather low accuracy and high spread, so the target must be very close in order for all shots to hit.