KC / KD shells - durability ?

[mr_timm]

How are people finding durability on shells?

I've been running KC and KD and am puzzling over getting cracking coming from the front body clip hole (both KC and kD shells have split from this point) and the rear point on the KC.

This is from say about 4hrs total of run time (say 40 batteries).

Haven't had cracking as an issue on the KF2 bodies so am wondering why it's happening.

Notes; was using body clips for first two sets of breaks. Ream the body clip hole with schumacher tool.
Switched to velcro having had two bodies break and am now puzzling over yet another break.

This is running at shrcc/epr/dms