Reflex Coil

The Reflex Coil mod increases your melee weapon's charge speed by 10% per rank for a maximum of 60% at rank 5.

Each charge attack is made up on both a charge component (which causes your Warframe to flash twice which is then followed by stamina being reduced for the attack) and then the swing component where the weapon is swung at the enemy.

Reflex Coil only affects the charge component of your attack reducing it using the following formula:

Effective Charge Time = Base Charge Time / (1 + Mod%)

For example, if you use a Gram (Base Charge Time of 800 ms) with a Rank 2 Reflex Coil (+30% charge speed), your Effective charge time should be approximately 615 ms (800 / 1.3).