I think it is neither. I use 844 I got from Wideners, and have used CCI #41 and Win SR. These are all quality components, so I think you have something else going wrong.
Your symptoms could describe mistakenly packed WC872, but not real 844.
Storage conditions and contaminants come to mind next.
Your load does sound very light. I would keep working up. I have used as much as 28 grns with 55 grn bullets, and 26 with 75's. Just watch for pressure signs.
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