This modification is best suited for predator defense firearms! 
The action must be positively cycled to reap the benefits of this modification!
 
ADVANTAGE:
A heavier carrier dog latch spring will improve feeding reliability.
Its purpose is to lift the round coming out of a magazine tube up to be guided into the chamber. The heavier spring will do this more positively.
 
SACRIFICE:
A heaver carrier dog latch spring will cause increased resistance when cycling the action. The increased resistance leads to rougher feeling slow cycling.
 
The standard carrier dog follower spring is silver.
The Remington 870 Police carrier dog follower spring (from the model 1100) is black.