After you get out of the prison in gears of war, when do you get back your hammerburst?

Question

And when do you first encounter grenaiders?

Answer 1

Hammerbursts are extremely common among enimies during act 1 and 2, so you can find them just by killing an enemy. Grenaiders don't really exist, locusts will usually either toss greeenades when you're behind cover, or hop over your cover and attempt to chainsaw you. You won't encounter many grenade throwing locust till act 2.