Magazine requirement is based on the base magazine of a gun. If the magazine is increased above 6 on a weapon that has below 6, it will still not be usable on that gun. However, if a gun has a magazine above 6 and it is reduced below that, the mod will still function.
If utilized with a burst fire weapon, it will not work with final shot of the burst. Additionally has no effect on the alt fire of the Azima.
Despite the above limitation, if used with Fusilai the 3 knife spread alt fire all three knives will be affected by the multiplier.
If Dual Toxocyst's last shot is a headshot, the subsequent 'free' shots will all be affected by the mod until the buff is lost.
With the set bonus, you can swap back and forth to re-fire the gun with one shot. However you need to wait the full second before swapping back or the automatic reload wont occur.