Breaking bottles?!

Within the past couple weeks I've had 3 different bottles break on me when I went to uncap them. The top centimeter or so of the bottle sheared off along with the cap. In all three cases the remaining beer was completely flat, telling me that the bottles must have had small cracks preventing proper carbonation. The bottles were from two different batches, neither of which were particularly overcarbed (one of the three came from a batch that I probably put about 10% too much corn sugar in at bottling time, but the batch containing the other two is undercarbed if anything). I never keep screw-top bottles, so that wasn't the problem either.

Has anyone else had the top of their bottles crack off? The only thing I can think that might be the problem is that I'm pushing down too hard with my wing-capper at bottling time. Any thoughts?

JB

I had a bottle crack when opening, and I have broken a few with capping.

My problem was that I was pushing down to hard. With the wing capper pushing down doesn't seal the bottle, pushing the wings down does (if that makes sense, the capper basically pulls the bottle up into the cap). Do the wing motion in your hands without a bottle to get an idea of how the parts move, and then focus on just moving the levers without actually pushing down on the bottle.

Sam Adams and DFH, I believe, went through a period with some defective bottles.

Had some redhook bottle's break exactly where you described. I started noticing indents in my caps and realized my brew buddy was pushing down hard while capping our bottles.