CALCULATIONS

+30% sprint speed with [Rush]
+397% strength with [Energy Conversion] and [Growing Power] activated

Infested mobility applies an additive +238% sprint speed to the +30% sprint speed giving a total 3.682x sprint speed increase which is multiplicative with the speed boost from [Volt]'s speed.

Speed applies a multiplier of +75% x 3.97 = 1+0.75x3.97 = 3.97x, and arcane phantasm adds an additional +60% to make 4.57x.

The total sprint speed multiplier therefore is 3.68 x 4.57 = 16.8x

If we add additional external sources like [Karyst Prime] (+10% movement speed) with [Dispatch Overdrive] (+60% movement speed on heavy attack), [Amalgam Serration] on a primary weapon (+25% sprint speed) and the Parazon mod [Runtime] (+75% sprint speed), we could theoretically [Reach] 20x + sprint speed solo, without relic fissure buff or team buffs.

Why not use more sprint speed mods like [Armored Agility], [Speed Drift] and [Sprint Boost]?
This is because the power strength bonuses from [Augur Secrets] and [Growing Power] scale sprint speed higher when infested mobility is applied.
You could replace [Rolling Guard] with [Power Drift] for even more power strength, and this would still be better than [Armored Agility] or [Speed Drift].
If you have an aura forma and don't like the conditional nature of [Growing Power], then use [Sprint Boost] in the aura.
[Narrow Minded] can be swapped for [Armored Agility].

Why not use molt?
This is because molt gives a bonus to movement speed which is additive to [Volt]'s own speed ability, giving overall less speed boost compared to infested mobility.