If I read your legend correctly it looks like R1 & L1 crossed And R2 & L2 did not. Did you clean the bores after the first round or did you just reload and shoot the second string. I would not discount 1f powder if you have any. From what I have read the rounded groves in your bore where there to reduce powder fowling. JMHO 1F may be more suited to that style rifling.