I put a weapon mod on my weathered 10mm pistol and it bugged the gun. Instead of having the gun equipped, it just shows a big red box with a white exclamation point in it around me.
I reverted back to my last save and put my class mod on my regular 10mm pistol instead.
Whats up with this? I really wanted to add class mods to my weathered 10mm because it seems to be much better than regular ones.
Does this happen to everybody with the weathered 10mm?

I've had the exact same issue with modding this weapon. It is still useable, however it makes it very difficult to see as there is a giant floating sign over your character whenever you unholster the weapon.

Here is a video I made of this happening.

http://www.youtube.com/mrverrsa#p/a/u/0/jW8nWa9DQ3k

Ive had this exact issue happen as well. Mine is a White box with a red exclamation point tho =p. Really hope theres a fix soon!

What kind of mod did you guys use?

I suffered from this as well. I added a silencer to my Weathered 10mm, but I don't believe the game has a graphic file for any modded Weathered 10mm, thus the error box denoting the lack of a graphic. I'd be happy if they just told the game to use the same graphics as the regular 10mm, so long as the Weathered becomes fully useable in-game.
While it's entertaining to watch someone fire an invisible pistol, I'd rather actually see my gun. Plus, I would really like to not have a transparent colored box obscuring my view when I try to use the weapon.

I used a laser sight with the 10mm.

Has anyone tried adding a mod after starting a new game post-update?

I'll start over if it works.

It's not a mod the game is just glitched. The red polygon you see is the default graphic to let you know there is no graphic for the object. My guess is that the classic pack items were never intended to be altered which is kinda lame. Why won't they release an update to fix it?

Yeah. I'm guessing the preorder packs weren't worked on. The weathered 10mm seems to be fine without any mods though.

It was the laser sight mod that did it to mine.