Perhaps the loose primer is possibly a badly cut primer pocket? Some of the early brass was known to have dished heads and pockets that were inadvertently cut with a slight taper. The flash holes looked a bit suspect too, especially looking into the case from the mouth, where they appeared to have a recess in the brass around them. This early brass generally had brass coloured primers as opposed to the later good brass with nickel coloured primers some batches of which were crimped in. One of the problems with the faulty brass was gas flow around the primer which can score the bolt face.
It could be worth measuring the outside diameter of the case head to see if it has expanded. I once get stellar performance out of a 308 with way too much H4895. I only notice that I had junked the brass when it would no longer fit into a shell holder! It had grown about 0.004" and primers could be pushed in by thumb.
If it hasn't grown then I would be tempted to find a slightly larger primer that does grip the pocket and carry on.
I too had the case bulge above the web, but brass is still going strong 5 max pressure reloads later. I haven't reloaded my necked PRVI brass enough yet but it has not developed a bulge yet. Maybe more indication the Hornady stuff ain't all that great? According to Saubier.com the Hornady brass is actually contracted out and made by Sellior & Bellot.
I have only tried both N110 with the 17gn bullets and it went well to 10.2gn where I stopped testing. I tried N110 and N120 with 20gn bullets, where N110 had the edge in accuracy and extreme spread at moderate speeds but as I pushed faster it quickly went to pot. I have had best performance out of Lovex D063 in 20 and 25gn bullets. If you can find some as reckon that is the powder to have.