Surefire X300U-B Sheared Pin

[PureBS90]

So today at firearms training I had an issue with my tried and true Surefire X300U-B. It is mounted on my issued Sig P227 and on the first shot of the training, my Surefire’s pin sheared and the weapon light fell off my rail. I have had an issue with it staying secure on my rail last year and it didn’t fall off but was definitely loosened after the day of shooting. I’m not sure if I need to locktite the threads to help but today when it sheared completely off and fell from the rail, I was a bit discouraged. Has anyone else had any issues with the locking pin shearing?

I have the correct Surefire attachment for the rail on my Sig. it’s not M1913 and I’m not sure if the Sigs curved rail design has contributed with it weakening over time or not. I secured my X300 tightly, not overtight but secured. I’m not sure if it’s the issue with the P227 rail or the pin in the Surefire.

Also, would the X300U-A or X300U-B be the best for Sig’s rails?

Respectfully submitted,

Blake

[Defaultmp3]

Also, would the X300U-A or X300U-B be the best for Sig’s rails?

It's my understanding that the consensus is that the X300U-B is preferable for any metal rail, such as on your P227 or on a quad rail for a rifle, while the X300U-A is better for polymer rails, such as on a Glock or maybe an MOE rail piece.

I have had only one crossbolt shear on me, out of multiple examples (one X400, four X400Us, four X400UHs), and it happened very quickly after getting it; I believe that there was also a batch of X300U-Bs that had this problem when they first came out. IIRC, they blamed it on a bad run of bolts, heat treat made them too brittle. Not too sure about the locking pin, although I assume that it could have the same issue.

[MisterHelix]

I sheared the pin on an X300U-B while tightening it down on a rail.
I called Surefire and they sent a replacement pin (free of charge, if I recall correctly).

Haven't had any problems since, but I don't tighten it down as much anymore, and I use a penny instead of a screwdriver.

[PureBS90]

I read on another forum that recommended the X300U-A for polymer rails and X300U-B for metal rails. Which makes sense to me, the metal rails can be tightened without messing with the integrity of the frame while polymer rails you wouldn’t want to over tighten.

[PureBS90]

I sheared the pin on an X300U-B while tightening it down on a rail.
I called Surefire and they sent a replacement pin (free of charge, if I recall correctly).

Haven't had any problems since, but I don't tighten it down as much anymore, and I use a penny instead of a screwdriver.

I’ll have to try this. I have always used a screw driver but never torqued it down too hard. But perhaps I’m too tight still.