The Assault Stubber has the same damage and armour pen as the Heavy Stubber, which is why I picked it, while still being a basic weapon.
Another option are Armageddon pattern autoguns, detailed in Dark heresy's inquistor's Handbook. A locally produced autogun variant, it has a smaller magazine and lower rate of fire, but is far more reliable, and hits harder. Vanheim Pattern Automatic Combat Shotguns are likewise a good buy at the same availability. FOr one rarer, D'laku Crusade Hellguns can be provided to officer units. Although the penetration is lower than post, it fires on automatic and can load from standard lasgun charge packs.
If toxins are a possibility, Panimune dosages will greatly increase survivability.