All clothing procs are only triggered when that clothing slot is hit when you take damage. So...
These are actually half broken. Sweeps and Anti-pills remove the ballistic damage buff.Edit: pic
That 7% chance of them activiting isnt that great when its 1 vs 1 but I suppose when there are multiple hostiles al shooting at you it will seem alot more. At level 39 you only gain an extra 9pts of ballistic damage which isnt much to get excited about as it isnt all that noticeable.
The pre-nerfed ones were a lot healthier. 20 or 25pts, I believe it was.
Unfortunately, they are no longer available.