A quick search turned this up; not Mach 2, but HMR, and not CCI, but Hornady. The principal is the same I think, however.

This is from another forum and is the response a guy got from Hornady CS:

Well after 2 weeks of not hearing anything I finally called them. I left a voice mail to a Cindy and got an e-mail back the next day. They supposedly lost my package and below is a Copy / Paste from the E-mail I got back from Cindy.

Mr. Pearson,
I'm sorry, sir, but we have no record of receiving a package from you. It must have been lost in the mail.
The 17 HMR cases may crack because of the annealing process when they are made. The annealing process is what makes the material brittle or flexible depending on the length of time and degree of the process. This is a precise procedure with any other case that can be reloaded, as we want the case to be hard enough to do the job but soft enough to stand up to several reloads. The 17 HMR case is dispensable and can not be reloaded, therefore the annealing procedure isn't quite as strict as with other cases. When the case cracks, it's because the neck was annealed a little harder than it needed to be, making it more brittle. This does not affect the accuracy or performance of the ammunition. Normally, the fired case will eject the same as any other, and unless they are picked up later, the shooter may never even know they had a case with a split neck. We would prefer that none of the cases split, (and the majority of them don't), but it seems redundant to spend the time and money on perfecting the case when it isn't practical or necessary. Our lab has evaluated cases with cracked necks, and the powder is fine, the case necks are just more brittle.
I hope that answers your questions. Please feel free to contact one of our techs who are much more familiar with our bullets, cases and ammunition than I am. Most of our technical personnel are at the Grand in Ohio this week, but will be back next week. They can be contacted by email at webmasterhornady.com or by phone at 1-800-338-3220.
Cindy

What fresh Hell is this?