Which primary weapon??

[Kaname Madoka]

I have the Crystal Mega Destroyer, which I don't use much, so is there better options? I don't know whether I should just get the Peacemaker or other primary weps.
My other loadouts:
Secondary: Crystal Fast Death
Melee: Skeleton Sword(to be upgraded)
Special: PSR-1
Premium: Golden Laser Cannon
So which primary weapon do you recommend?

 

[???]

Either the Rambos rifle-Combat rifle upgraded fully or the eindringling but if you like to run and gun Marksman M2

 

[Serendipity]

Rambo's Rifle (Less Mobility/3HKO Head)
Marksman M2 (High Mobility/4HKO Head)
Peacemaker (MACHINE GUN WITH NO RECOIL)
Deadly Candy (1HKO Head Shotgun)

 

[Recon]

eindringling, its 3 shot head which is op,
rambos and marksmon are both 4 shot