These extra-power striker springs make the striker move faster and hit harder to reduce misfires and increases lock time. To the shooter, the faster the firing pin strikes the primer, the tighter the group.
Extra power striker springs decreases the "lock" of the rifle. The lock time is the amount of time from the moment the striker is released from the sear until the striker hits/ignites the primer. The shorter the lock time, the shorter the time the rifle has that it can move off of the target.