Renaissance Robot posted:

Walk turrets towards them. So like, plonk down half a dozen turrets and load them up, then stand next to them and place six more as far out as you can, remove the first ones, rinse and repeat. It's a bit tedious without blueprints, but it's the safest way to advance on biter spawners without heavy weapons (PS the rocket launcher isn't actually all that great anyway, because you can only use one at once )

If that sounds boring, you'll do better building a shitload of defender capsules, getting in your car, and doing donuts in the general area you want to hit.