Seeker Six

Seeker Six breakdown (First with no damage skills, then what damage skills change):
Bodyshots on a dud:
Clots
Sirens
Crawlers

Bodyshots on an explode:
Sirens (If it doesn't hit metal)
Gorefast

Headshots on a dud:
All above, but NOT Sirens
Gorefiends
Bloats
Alpha Clots
Husk Backpack (but not head)

High Impact Rounds vs Bombardier
They both let you 6 shot Quarter Pounds, and 1 shot Alpha Clots, but Bombardier can hit a metal arm, and still kill in 6 shots, and High Imapct Rounds is inconsistent at killing Alpha Clots while locked on, you usually need to aim lower, and fire manually in order to kill. They both let you headshot Sirens on a dud.

High Impact Rounds + Bombardier
Kill Bloats in 2 explosive body shots, a chance to kill Husks in 2 explosive body shots depending on splash. Explosive damage applied last, meaning Bloats won't spawn shit when killed this way. Make helping with FPs less of a joke.

Armor Piercing Rounds alone
Dud headshot sirens. Can kill a Quarterpound in 4 weakpoint shots, 1 arm, and 1 body shot. 2 arm shots means you can't kill.

Armor Piercing Rounds + Something else
Kill Quarter Pounds a little more consistently

All 3
Headshot Husks in one dud. Kill QPs in as few as 5 shots depending on aim. Better odds of killing FPs in 2 clips.