Well, I've since replaced the factory stock...
Old Version:
New Version:
Using ANY LED "drop-In", I'd go with a Z44 (regular bezel)., and with a Shot-Gun, I'd stick with a quality one as well, as 12ga. recoil is A LOT more brutal than 5.56/.223.
A few other options for home defense (i.e. the gun w/ light that doesn't get shot 100 times a year) would be a dedicated LED bezel from SF, including the KL5/KL5A, or in the case of the 918FA (shown above), a KL6. This would work in a jif if needed, but I wouldn't "practice shoot" with it, as these bezels were never sold/tested for use on a weapon, but they should hold up to the 3-4 rounds you may have to put-out in the event of a break-in, etc.
The factory 618 came with an L60 body/Z32 bezel/P60. This pic shows the recommended set-up of the L60 with a Z44 (replacing the Z32 Shock isolated bezel). Please note, fro My experience, the size of the Malkoff makes a tight fit in the L60 body, and you may have to shave the malkoff down for a good fit (or stretch the contact spring).
Shown here with a KL5 on the L60
However, SF is coming out with a replacement for the KL6 (9V Millenium Series LED Head), and this one is advertised as being useable one weapons.
Also, for practice or even special applications, you could use the KX3 (three stage LED assembly found on the GxD-FYL lights)