I did the test using shotgun Felwinter's lie, perk "Who's next?" -it doesn't need to be the last bullet on your magazine, you just need to reload right after a kill, -the buff last few seconds and decay, so don't use it on your last bullet, you wont reload the 6 bullets equal fast, -besides it feels that the benefit stuck with "flared magwell" (quick reload) on same shotgun, so you can pick any other skills instead like "snapshot"