Originally Posted by Ed_
On my second batch I used a 6.5 gallon plastic bucket for primary with virtually no problem and will be using the 5 gal carboy for the secondary.
I got away with this for a couple of years until my last batch. I had a fermentation so crazy it blew off through my 6.5G bucket. Not a major explosion but enough to make me think I should use a blow off tube even with a bucket in the future - especially if it's 5.5G or more in the bucket...