Thread: .17HMR bolt gun splitting cases

Originally Posted by Matt2308

To fix it will probably require re-chambering with a reamer with tighter tolerances.

I've been down that road with a .17m2, in my experience if you've got a batch of ammo that splits then re-chambering doesn't solve it. Factory chamber, re-chamber of factory barrel done by Arthur Cleland, Clark Custom barrel from the states, custom barrel put together by Dean Maisey - all would split cases with certain lots of ammo. Other lots of ammo will be fine, and newer ammo is likely better.
I have seen split cases coinciding with low fliers on the target with a certain batch of ammo, but most of the time the split doesn't seem to have any effect.
All .17hmr is manufactured by ATK (CCI), other than Winchester. Sellier & Bellot used to make it too but dropped it.