For each Interval/Score achievement you will need to maximize your points gain. This is easier without a partner as your individual score is needed to earn this achievement. Interval 05 introduces the next step in evolution for the ATC forces, these guys will take more to put down but some have tanks on their back you can use to kill. You will also face off against a few waves of psychos here. You can get 7 or more weapon challenges here (Strader, SMG, CAS, G3A3, Frag/Flash/Shock, Schuller, Penetrator, Riot, Laser). The big challenge in this level will be fighting against a Phase Caster and then a Powered Armor immediately afterwards. Like the Powered Armor in Interval 04 you should use Shock Grenades to stun him while you hit him with everything you have.