Raider suggestion

[Cassey]

I'm sure this is pretty obvious, but wanted to mention it all the same:

Playing "regular mode" (Ideal for first game?).  In cycle 3, around day 9, and the Raiders are hitting me with M-24s.  Those have a range of about 2X what my turrets have, so one guy can pick off all the turrets.

Only defense I've come up with is to have everyone attack the M-24 guy melee style. 

Anyhow, presume we will get turret upgrades later?

[Dragula]

Make a wall around you colony with a one or two-wide opening. Make a second wal so you have a narrow corridor leading to the opening.
Now place your turrets, sandbags etc so the snipers come within firing range of your weaponry. You could even put sandbags in the corridor to slow the raiders. Hopefully it's clear enough, I can post a screenshot when I'm home