I know there was a thread about cracks appearing in the fiber optic housing on ACOGS. DId anyone find out what was causes this? I'm thinking quick temperature changes. I have TA31 and never noticed the cracks until looking the scope over one day. The scope functions fine and the cracks don't seem to go down to the fiber optic.

I'm guessing temperature changes because I just got a TA31F from Fedex today. I was shocked when I opened the package to find a TA31F. I had backordered Monday and was expecting a loooong wait. I opened the package and examined the scope. I noticed it felt kind of cold to the touch. The first thing I looked at was the fiber optic housing it was perfect. No cracks whatsoever....for about 5 minutes. Then I noticed the cracks starting to develop right before my eyes.

Its about 70° in my house and in the low 60's outside and probably in the 40's or 50's at theFedex facility where my scope was loaded on a truck for delivery this morning.

Like I said my TA31 is fine so I'm not too worried about the 31F. Just an observation.

You might be right.  Mine seemed to crack on very hot days insibe my jeep.

MY guess is that is comes from temp changes.  Thats said I had my TA31 in the bottom of an aircraft and it was frickign cold and then out on the tarmac in the UAE (at 50 something celcius in the shade) and it suffered no ill effects (it has tiny crack lines but nothing oozing out so not worries right...)  It sat around doign some nasty (for me) temp changes from day to night in Afghan and still is okay...