Kristen, I think you got mega cartridges rather than mega cartomizers. Those will only fit on the mega atomizers.
I love those sample bottles too! I never even frown at getting a sample of something I already have just because I'm excited to have another bottle. LOL
So when you do your fill sessions, how do you keep track of what flavor is in the carto? Do you use labels or what? I have a feeling this is what I should probably be doing so I can get the maximum amount of fluid into the carto to start with.
The revision 2 & 3 didnt' work for me either, but just got 100 in from www.e-liquid.cn and have to say they work great. None of the issues the first ones had. Best at HV of course but on a 900mAh ego they work better than any cart i ever tried. The XLs hold a lot of liq at ~1.7ml. 510 attys wick so poorly i could never get more than about 10 minutes of vaping even from the mega carts. FWIWThe CE2s didn't work for me Kristen, but since you have an ego, the ego mega cartomizers hold about the same amount as the CE2s.