A buddy of mine is a real HK junkie. He has the Mark 23, USP9, USP45, USP45 Compact, USC and P7M8. He also has the UTL which fits on the USPs (but not on the Mark 23, sadly) and we have done low-light work in at his pistol club in Elsmere, Delaware.
When it comes to whether to have a tactical light, the answer is always yes. Many encounters are in low light or complete darkness -- remember rule #4, you must know your target and what is beyond it at all times. You cannot comply with rule #4 with night sights, as they will not illuminate your target.
However, a related question is whether to use a weapon-mounted light. For a long arm, the answer is always a resounding yes. For more on low-light operations with a long arm, see John Farnam's "The Farnam Method of Defensive Rifle and Shotgun Shooting" and Gabriel Suarez's "The Tactical Shotgun" and "The Tactical Rifle".
However, for a handgun like the USP, it all depends on whether you carry concealed outside your home. If you do not carry outside your home, a weapon mounted light like the UTL or the Surefire Classic/Millennium is recommended, over a separate flashlight like the Surefire 6Z/6P or the Streamlight Scorpion. This is because a weapon-mounted light will make it much easier to clear malfunctions, reload your weapon, and in general will leave you one hand free for guiding noncombatants or dependents to your safe room, opening doors, shutting windows, etc.
If you carry concealed, you will want a separate flashlight. Most likely, you will not be wearing a Blackhawk Omega VI-L holster on the street (designed for handguns with integral lights) so you will be using a separate flashlight for the street. Avoidance of cognitive branching pitfalls demands that you do not take on two training schemes for the same situation (i.e., one method of operation for home defense and one for street defense in low light).
Thus, if you carry you should use a separate light and train exclusively with that particular system, home or away. Malfunction drills and reloads are more complex, but are possible.
Check out Firearms Tactical's improved lanyard for the Surefire 6Z/6P -- I have one and it is useful for retaining the flashlight when two hands are needed for misfeeds and the like. Otherwise, Gabriel Suarez in "The Tactical Pistol" recommends putting the flashlight under your dominant armpit while you clear the malfunction or reload your weapon.
In all instances, whether you use a weapon mounted light or a separate light, you should adhere to the set principles of low light fighting. Flash, shoot and move. Use indirect lighting (e.g., bounce the light off the ceiling to illuminate an entire room with one shot) instead of direct lighting when possible. And avoid using your flashlight as a search light.
Since we have carry here in Pennsylvania, I use a Surefire 6Z with the ITL and P61 (120 lumen) lamp assembly, carried in the pocket. When clothing is a problem, I use a standard Surefire 3P.
HTH,
Justin
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Justin T. Huang, Esq.
late of Kennett Square, Pennsylvania
