Red dot glass shattered while shooting- need help figuring out why

[CC3D]

Long story short- I had my TSO milled for a Romeo 3 Max in preparation for limited optics. This is my limited gun that I'm converting over so it's currently chambered in 40. I plan on shooting .40 minor for a while while LO is getting going. 

 

That being said, I went to zero the dot today with some of the remaining .40 major rounds I had loaded up. I know long term .40 major is probably not the best for longevity of the dot, but after firing the first EIGHT rounds, my glass is cracked. 

 

 

Originally I thought my brass was ejecting and hitting the glass causing it to break (can this even happen?) but after taking some slow motion videos, and placing tape over the dot to see where the brass was contacting I could not see any evidence that the brass was hitting it. The larger crack is "scalloped" out of the front of the glass, but the smaller bit in the bottom right is on the inside where the brass cannot contact. Again, I literally fired 8 rounds though the gun before noticing the damage (it could have been less that actually caused it)

 

I'll be reaching out to sig to see about warranty but I wanted to see if anyone could help me out here before I talk to them. Is this from the brass? Recoil too much for the dot? Did I just get unlucky with this dot? Any help is greatly appreciated. Thanks all

[shred]

I had one crack sort of like that when it got dinged.  Took me a few shots to notice since I was working on target focus at the time.  Haven't seen it happen in use ever.

 

[CC3D]

 

28 minutes ago, shred said:

Haven't seen it happen in use ever.

I’m wondering if it’s a combination of a weak dot and the .40 sw. these are comp loads around 170pf so definitely lower than most factory. I did buy the dot used but it looked untouched. Unsure if the dot’s history is contributory. 
 

Also running relatively light recoil spring properly tuned for my major loads. We’ll see what sig has to say tomorrow but i dont want to just throw a new dot on and hope this doesnt happen again- i’d like to have made at least some sort of adjustment 

[BritinUSA]

One possibility: As the crack is right on the edge of the glass, I'm wondering if the scope has been over-tightened so that the scope body/frame around the lens has been warped enough to cause a stress fracture of the lens.

[CC3D]

1 minute ago, BritinUSA said:

One possibility: As the crack is right on the edge of the glass, I'm wondering if the scope has been over-tightened so that the scope body/frame around the lens has been warped enough to cause a stress fracture of the lens.

Interesting. Apparently others have had issues with glass breaking on the 3 max- hopefully sig will have some more insight. 

[shred]

I run them on 2 Major Open guns and 3 slide-mounted minor pistols, The main failure mode seems to be buttons on the Open guns (after 3+ years) and windage adjustment on the slide mounts (variable.. some much better than others).  

 

Sig's warrantee has been very good every time.

 

[caspian guy]

I had that happen with my first Romeo 3 Max (chip popped out at the top of the lens) I was using a converted rts2 mount on my open gun that had been relieved around the foot print of the sight body to allow it to fit (snug fit as the rts2 had been) also it had no recoil boss pins in the base.  After Sig replaced the scope under warranty I switched to mount that didn't touch the body of the scope on the sides and had recoil boss pins in the base.  Other than the buttons starting to go bad (which I'll have to send it back for soon) it's been good for a couple of years.

[Sestock]

That is why people who have slide mounted optics on open guns have 4 optics.  One on the gun, one spare and two sent in for repair.

[Racinready300ex]

Everyone I know that's run sig optics in CO has broken them. None have been cracked glass, but all have been fixed by sig. 

[CC3D]

Sig seems fully willing to help with repair/ replacement. They did not yet have anything to say about what causes this damage. I'll only be putting minor through it and am considering a stronger spring+ buffer out of caution but wish I could get an answer about what directly caused this issue so it can be addressed and hopefully won't happen again

[konkapot]

CC3D I suspect that there are going to be a lot of people putting dots on their .40 limited guns. You're a trailblazer in the field. Hopefully it's just an issue with a particular dot and not a "dot on a .40 limited gun" thing. 

[zombywoof]

I had an RTS2 lens crack on a new open gun during initial sight in, less than 30 rounds.

 

I chalk it up to manufacturing defect. The replacement has lasted for years.

[CC3D]

6 hours ago, zombywoof said:

I chalk it up to manufacturing defect.

I am hoping to too- regardless I do not plan to run major on this dot ever again out of caution

[MikeyScuba]

On 4/27/2023 at 2:40 PM, Sestock said:

That is why people who have slide mounted optics on open guns have 4 optics.  One on the gun, one spare and two sent in for repair.

Old school slideride for the win here.  While I do have a backup, I’ve never had to use it.  Only optic issue was the windage screw loosened and vanished on one of my blasters.

[CC3D]

Slight update- sig has shipped a new optic out so we're good there. 

 

I took the gun out to the range yesterday with the heaviest possible spring and a buffer. Ran 200 rounds though it of .40 major and the optic didn't sustain any further damage whatsoever. 

 

At my previous range trip with underpowered recoil spring every few shots would increase the damage further and further. This is telling me the slide energy was too much for the optic to handle but running .40 minor in the future will likely be perfectly fine. I'll run a buffer to be on the safe side for a while and post another update once I get the new optic on the gun. '

 

Thanks to everyone who replied!