There is absolutely no way you are going to have a useful range of 300m. You MIGHT be able to see something clearly at 100m - beyond that you are going to possibly see something but as I said, it will not be lit up very well at all.
If you want the best light with a side switch, I gotta recommend a Zebralight SC600. Easily the most used light out of the 10+ units I own.
Yeah, you aren't going to get the range you want but do you really need that much range?
Unless you have a specific task that this light will be solely used as that requires that range, I urge you to reconsider.
After a few years of just buying whatever light grabbed my attention I soon realized that there's more to it than overall output and such.
If you need illumination range you really can't go past a modded TN31 from the one stop throw shop..