Originally Posted by
JMS
It's been hashed out on LF quite a bit, in both holster-specific and light-specific threads. They can be found within the Stud Board, First Line Gear, and Low Light subforums.
The 300U will fit SF holsters for the 300, but the extra length of the 300U head CAN (not WILL) result in the thing bumping into the disc at the bottom of the light channel, perhaps making the gun stand apart of retaining. As that disc is only held in by friction, it's easily removed and the problem solved. If one is worried about losing that little extra layer of protection for the light's lens, one should replace the holster or stick with the regular 300.
They're responding well to the introduction of the300U, but if you use a DG switch that's been out for, like, CENTURIES, it's still about 50/50 that one'll have to dremel or heat-gun the stinking light channel so that the bloody thing fits, regardless of whether it's a 300 or 300U.