Mine runs good on the Winchester 555 bulk packs. In the past (up to 25 years ago) I have found that some of the lower end (Blazers, Wildcats, etc) are weaker and do not operate the slide correctly such as you describe. I would do as HAL suggests with the Stinger case and try some CCI or Winchester SuperX ammo. Surely you can find some bulk pack ammo that will serve for range and blasting if desired once you prove your gun.
Thanks for the tip HAL.
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