That is the likely culprit, thinking about it more. All three blew out in exactly the same way, and were drilled, painted, and glued as part of the same batch. I think what happened was this--I'd used a little WD-40 to lube as I drilled (this was the batch right after the one where I got the drill bit stuck--see link above) and then I painted the blank with white acrylic. I don't think I cleaned the WD-40 off the blank sufficiently and so the paint and the glue did not stick well when I put it in. I think I may just use a little water and detergent for my lubricating liquid from now on, then rinse with water, and blow dry with compressed air. I'm also going to try painting the tube with modeling enamel rather than acrylic. The enamel seems to adhere better and gives thinner, more even coverage than the thick acrylic paint I'd used on the blanks that blew out.Personally I find when I'm blowing out blanks it's a glue issue
. . . I'd used a little WD-40 to lube as I drilled (this was the batch right after the one where I got the drill bit stuck--see link above) and then I painted the blank with white acrylic. I don't think I cleaned the WD-40 off the blank sufficiently and so the paint and the glue did not stick well when I put it in. I think I may just use a little water and detergent for my lubricating liquid from now on, then rinse with water, . . .