How do I get bullets to kill the beasts?

Bullets = energy points. When you click on the beast, a circular spin wheel will appear, highlighted in green. In the lower right area of the wheel is a pointer ending in a circle. The number inside the circle tells you how many energy points one shot costs. When you have enough, click the pointer to shoot/spin the wheel, & see how well you fare. In my experience, it averages around 10 - 15 shots to fell a beast, but your milage may vary. I originally built the weapons factory because I thought I could buy/build firearm upgrades that would make me more accurate, & cause more damage, so I'd need fewer points per shot, & fewer spins. Silly me.:(.