Yeah, this.
Because...
Armiger Warglaive
T9, 3+/5++ (Ranged Only), W14
Armed with Heavy Stubber and a Thermal Spear
Does an average of .11 damage outside of 18", 1.26 in 9"-18", and 2.44 under 9".
Takes 25 turns of Melta Range firing to kill a Manta.
Manta
T14, 2+/5++, W60, cannot be charged since it's an Aircraft.
Armed with two Heavy Rails, six Ions, two Long Burst Cannons, two Missile Pods, and ten Seeker Missiles.
Each Rail does 3.67 damage on average, but more accurately has a little under a 1/3 chance of doing 12 damage.
Each Ion does 1.08 (normal) or 2.17 (overcharge)
Each Long Burst does 2.67.
Each Missile Pod does .33.
Each Seeker (one shot) does 1 damage on average.
So that's just over 19 wounds on average, before Rail Rifles (highly swingy) and Seeker Missiles (limited ammo).