What is best nerf spring gun with mods?

Hi, im looking to buy a good spring gun due to their faster fire then singled air guns though im not sure which one is the best. Im looking for something that has high rate of fire, good power, fast reload. Something along the lines of a rapid fire shotgun, but modding those are a pain. I dont want a longshot. I was thinking something along the lines of a Pump Action Shotgun or a BBB but i would have to breech them myself, which i dont know how. Something like a firefly with turret mechanism but shoots good. I dunno...