not enough clarity re "testing"
shells didn't fire first time but SAME shells fired
when gun was re-cocked?
or
shells didn't fire but others did?
handloads cause many problems
Try quality factory ammo.
if there are failures to fire examine gun
first correct feel and function as suggested
then chambers
including headspace
( with extractors or ejectors removed and then replaced)
if factory ammo fires correctly then you have reason to examine
ammo that malfunctions
thin rims
primers
worn shells ( especially primer pockets)
