I'm currently debating between an M300C, or an X300U-A for my CQBR (DD Mk18 RIS II). Yes, I know a WMX200 (or M3X) would be clone correct, but I'm not willing to sell a kidney for a WMX200. I already have an M300C and I'm very happy with it, but the X300U offering twice the lumens for the same weight is pretty appealing (along with it being available in FDE).

I'd be running either one with thumb activation (I like to avoid wires and pressure switches if I can) at either 9 o'clock, or in the case of the M300C, 11 o'clock in a Gear Sector mount. Mainly I'm concerned with the durability of the X300U-A vs the M300C, and also whether it would possibly unintentionally discharge inside a soft case. I've heard of quite a few complaints regarding the battery door breaking on the X300U and, of course, the cross bolt breaking on the B model (really only interested in the FDE A model). While I don't abuse my gear, it does see some fairly hard use; even knowing SF will fix anything that breaks, I'd rather not be down a light waiting for a repair. I know the M300C is a tough little bastard... and it won't trigger inside my case.

Don't really want to mess with a pressure switch replacement door or pay for any kind of exterior body for the X300U. If it's going to cost more than an M300C (I can get both for the same price), or be significantly less durable without upgrades, then the extra lumens aren't really worth it to me; I'll just Alumahyde a black M300C in Magpul FDE and call it a day. Anyone with an X300U-A mounted on an AR care to offer some insight as to durability and unintentional discharges (especially in a soft case)? Any other observations from direct experience regarding the X300U on an AR would be appreciated as well.

Hard to read your post, here's my thoughts.

X300 is ok if you mount it on 12'clock with fixed front sight butted up against the tail cap. The tail cap is a significant weak link when mounted on a rifle.
The scout lights are superior for durability, the stock pic mount is excellent, and they are readily adapted if your needs change.

You didn't like my wall of text? Ha, there... should've broken it up. The CQBR uses a fold down KAC front sight, so 12 o'clock mounting doesn't really offer much extra protection. Plus, if I ever add an ATPIAL-C for NOD use, it'd have to go elsewhere.

Actually, reading over my post, I pretty much already know the answer. Just giving the X300U one last chance. It's FDE, 600 lumens and lightweight; I really want to like it :\. Maybe I was hoping someone would say, "Hell, no! I use my X300U all the time and it's never broken on me once! On the days it isn't on my rifle, I use it as a framing hammer on my construction job!" Oh, well... probably not. Thanks for the comments all the same.

The X300 series I've seen as more a handgun light.  They'll work on a rifle, but the m300 is more durable.  I'd go that route.

I ran a x300 for years at the 12 o'clock position with no issues however I like the scout lights better and have since switched to using them.  Very adaptable, very tough and very bright.  The ability to use different mounts without bolting on rails to a slick mlok rail is great.

I use M300/M600 on rifle. X300 is my backup to mount on lower front rail in case primary is dead. I tried a dedicated X300 and did not like the thumb contact area for a rifle. It's also not protected and accidentally activated in my bag. While the M300 has a prettier beam, consider an Arisaka 300 series. Does 350 lumens, costs $100 less than M300, weighs less than M300, comes in FDE sometimes. Out of stock at the moment but I'm getting another in FDE as soon as they are back in stock.

Yeah, that was one thing that worried me, that switch looks like it would be easy to trigger in a soft case. I did pretty much decide on another M300; I picked up a Gear Sector mount and a can of Alumahyde Magpul FDE over July 4th.

Hmm, didn't know the Arisaka 300 came in FDE. That might actually be a pretty good option if it'll fit the Gear Sector mount; I assume it will, I'm pretty sure Arisaka M300 bodies are interchangeable with stock SF mounts.

Just curious, are we talking about $100 less than M300C retail, or actual street prices? If street prices, that'd be like $90 bucks...

I guess I'll go price one out on Arisaka's site. Thanks for the suggestion.