Amalgam Serration - can be replaced with regular serration if you'd rather optimize as much as possible. I prefer the speed boost though

Primed Shred - can be replaced with vile acceleration or a mod that prioritizes punch through more, really up to preference

Hammer Shot - This one is really here to add as much crit as possible. Feel free to replace it with a riven that has better crit, or some other qol mod that you'd prefer

Vital Sense, Point Strike, Split Chamber - I'd consider these to be essentials. [Split Chamber], you could maybe replace with something that boosts fire rate, etc. instead. Really, you don't need that much fire rate though

Stormbringer, Hellfire - These are for radiation damage, with eidolons are weak to. No need for [High Voltage] or [Thermite Rounds], status chance isn't really needed. If you'd like, though, you can [Sacrifice] some heat damage to get a magazine capacity boost.

Primary Dexterity: Because Primary Deadhead doesn't trigger on synovias, Primary Dexterity is the best you can do in my opinion. Just go ahead and kill some nearby grineer caught in the crossfire, or maybe vomvalysts, if it procs on them. If you don't have a decently ranked dexterity, merciless is capable of putting out a fair damage buff, albeit requiring more kills than dexterity.