Thread: .17HMR bolt gun splitting cases

It's a common issue with 17hmr's and certain batches of ammo have also had issues with split necks in loaded rounds still in the box from the factory before firing.
I suspect that the brass they use is worked a lot to neck down to 17 cal and consequently hardens quite a bit and then when fired in a chamber that has slightly larger tolerances, it will be more prone to splitting.
To fix it will probably require re-chambering with a reamer with tighter tolerances.
You could try different manufacturers of ammo to see if one has slightly thicker brass which may fix the problem, but I believe most is made by the same company and just rebranded.