I have a problem which I think is related to the primer used. 7SAUM using VV N165, 61.2gns with 190gn A- tips CCIBR2 primer, speed is only 2840fps, after firing 3-4 rounds in testing I cannot chamber another round. This has happened twice now as the first time I thought it was a brass sizing issue. Looking down the barrel I see what appears to be a lot of either unburnt powder or residue. I'm assuming this is why I can't chamber a round after 4 shots. I tested with jump and couldn't find anything that looked good on paper so went to jam. So now I have this problem. Is it because I should be using CCI 250's.