After drinking a few bottles of my first batch I have noticed differences in carbonation levels bottle to bottle. Some are almost flat, while some have much more carbonation, or somewhere in-between. They all were bottled at the same time from a bottleling bucket with boiled priming sugar. Even though I haven't noticed any leaks from my bottles, and they don't twist unless cranked on extremely hard, my concerns are the bottle caps and capper used. I used the generic caps that came with a simple kit, while my new kit has a name-brand caps (DeGroen's) which appear to have a thicker seal inside of the cap. Can a better cap seal better? can a generic cap leak some carbonation? My capper looks like it is a mod creta or mod greta and seems to work OK. Any thing else I might be overlooking that might cause this?