It's funny, when life gets too busy it's often your health that gets neglected. I don't mean in the sense that no-one gets to the doctor but more that good diet and sufficient rest and exercise are all passed over. Ironically, I think these are the things we need most when life gets too busy (we also need them if we want to get giant guns).
So how do you get giant guns? Nope - not bicep curling 10 sets of 30 reps of 100kg (is that even possible for anyone?). You get big guns by doing big exercises. Start with the basics - your compound exercises - these are the ones that work out more than one or two muscles. Your bench press, squat, deadlifts, rows and a handful more (google it). Combined with consuming enough calories to allow you to grow muscle (this means eating more than you burn in your average day), and adequate rest (not just enough sleep, but enough time between workouts), you'll get big guns.
Then do your bicep curls to bring out their definition.
There's so much literature out there on this - it's worth a read. Or check out the local body building forums - lots of advice available.