How to unlock weapon attachments in Battlefield 3?

I've unlocked quite a few attachments by now but I don't know what unlocked them? I assume you just need to get a certain amount of kills with whatever youre using, but theres no counter or anything for you to track that. Mainly I'd like to know when you get the holographic sight...do you get it after the red dot sight?How to unlock weapon attachments in Battlefield 3?
you unlock attachments by gun by getting kills with that specific gun. you can't tell ingame what you're getting next, but while customizing kits, if you open up the primary weapon selection, there should be a bar that's partially filled with light blue. when it fills up, you've gotten enough kills and unlock the next attachment, the bar then resets.How to unlock weapon attachments in Battlefield 3?
as you get more kills with a certain weapon, you get more attachments for that weapon. there is no ingame counter for your kills, but there is a counter on battlelog which shows how many kills you have for each gunHow to unlock weapon attachments in Battlefield 3?
I think so!
you basically unlock guns and attachments the more you use that specific class