Donna:
Thanks for looking at this jacket for me.
I'm quite surprised that the base diameter is greater than the finished diameter of the bullet. I guess my measuring instruments aren't sufficiently accurate to pick this up. My caliper and michrometer each show the base diameters to be less than .358. Perhaps this is a manufacturing fault, or the dies may have bulged under pressure.
As to the "cracks", I've been of the opinion that these were actually fold marks which hadn't filled during the end flattening process. The original samples that Corbin sent me when they delivered my equipment, had these marks in the heel, and I had considered them to be something that wasn't avoidable.
As to the annealing process, I've heated to colours ranging from the recommended dull red, through bright red and an orangy red, and always got the same results with fold marks in the heel.
I've never contacted Corbin about this, since I really didn't think it was a problem - just a deficiency inherent in tubing jackets. I'm actually much happier with Butch's jackets since the cost is very little more than my material cost for tubing, and it saves me the time and tedium of making tubing jackets.
In order to close the hole in the base, I've simply been following Dave instructions by making sure I have some "piping" when I end round, and then using the end flattening die (and core seating punch) in my Series II press. I'd say the hole closes up over 50% of the time. In general, I've found that I have to use much more pressure on my press handle and dies when jacket making than I do when actually swaging cores and bullets.
Rick