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P226 MK25 issues with the Surefire X300 Ultra

18K views 13 replies 10 participants last post by  Amphibian 
#1 ·
I purchased a Surefire X300 Ultra for my MK25 and I can not get it to lock into the rail system. I've tried both the universal and picatinny connectors that come with it and neither one will lock in. I've read mixed reviews from other sources online, some say the picatinny will fit, others say the universal will and then others say it won't fit all because Sig used slightly different picatinny rails on the MK25.

Has anyone else had this issue? Any suggestions? I really like the light and would like to find a way to make it work.

Thanks for the help!
 
#2 ·
You may have to slide the light until it slips into a slot. Sometimes this can be a bit tricky. Also make sure the inserts are turned the right way. Some are angled and some are more universal.
 
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#3 ·
Thank you GCBHM. It slides on until the battery door hits the trigger guard. The notches on the light that lock into the rail are about 1/16" from being able to lock in. I've seen images of it on MK25's, so it appears to fit and I've seen people in here recommend it as a great light on the MK25's.

It is extremely difficult to get the light on and off the rails. This is my first Surefire weapon light, so I didn't know if that was normal or not.
 
#4 ·
Try loosing the allen screws on each side a little bit. Once it slides on then tighten them if needed. The mk25 uses a 1913 rail and I believe I used the default one that came installed, universal I believe.

I'll have to check when I get home to be certain which adapter I'm using.
 
#7 ·
This was going to be my next suggestion. It can be difficult to maneuver if the tension bracket isn't loose enough. I learned that one the hard way.
 
#5 ·
The MK25 is definitely M1913 Picatinny so any 'keys' for the M1913 should work. That's one of the main reasons I went with the MK25 over some of the other available Sigs because I didn't want to worry about scratching up the finish on the proprietary rail they have on everything except MK25 and Combat models.
 
#6 · (Edited)
It'll fit. Just use a little force to push the light far enough back onto the rail. I took my P220 Combat directly to Surefire since I couldn't get my X300 mounted and didn't want to risk breaking anything. Sliding the X300 back and forth on another mil-spec will help break-in the mount if it seems too tight. The tech at Surefire used the universal mount, which he said makes it easier to remove to light when you need to.
 
#9 ·
Hope those ideas work, I know that my surefire didn't fit on my sig's, well at least right, the back hit on the trigger guard radius such that they wouldn't mount straight/flat. Switched to streamlight even though I like the quality of the surefire better (not the price).
 
#12 ·
I haven't put my Surefire 300 Ultra on my MK25 but did put it on my P226 40 using the universal adapter. Did my testing at night with range lights off. On the second shot, the 300 took off and spiraled about 2 feet in front of me with a spectacular light display. I thought the P226 had blown up. Used the Picatinney adapter, an absolute ***** to put on and i don't think it's ever going to come off, no problems on the range.
The Picatinney does work but it is so hard to get it locked.-Dick
 
#13 ·
I got it to go on last night. I switched to the universal adapter and had to loosen the screws quite a bit to get it to lock into place. I tried the picatinny adapter, but no matter what I tried I was not able to get it to lock. It's extremely difficult to get it off without loosening the screws, which is a good thing I guess. Thank you everyone for your suggestions. I appreciate the help.
 
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