All 17 HMR ammo is made by CCI. The only difference between one brand and another is the color of the ballistic tip and the head stamp:
CCI, Federal, Winchester, Remington and Hornady all loaded here at CCI in Lewiston, Idaho with a V-max bullet are identical, with the exception of tip color. Manufactured on the same equip, to the same ballistic specs, using the same components other than color of the tip of the bullets. Obviously the shellcase 'head stamp' and packaging would be different on the various products.
CCI/Speer Technical Services
2299 Snake River Ave.
Lewiston, ID 83501
Buy the cheapest available. Now you migth have noticed brand differences in the past, but what you are experiencing is differences in lots. Retooling, different batches of components, etc. Look under the box to see the lot # stamped on the outside.
Call the CCI toll free number and talk to or just e-mail customer service.
They can track down the lot # of your ammo with neck splits and get you squared away.
You may even get the ammo in question swapped out for fresh stuff for free.
I've just always used the Winchester vmax because Varmint Al did a test on like 5 different brands in a .17 HMR and the Winchester gave the best results by far. It worked pretty well for me, so that's all I've ever used in my 17.