CptCurl was right regarding doubling. I was in denial there for some time but made a trip to the range today. My 440gn reloads didn't cause it but my 570gn reloads did.

So I have to repair the buttstock weight and the RH trigger meachanism. Just as well I bought a set of fine bladed hollow ground screwdriver bits. Anyone know where I can find a Merkel dissassembly/parts breakdown manual?

BTW - what would be the likely cause for the RH barrel firing with the left in regards to the trigger system? Sear engagement, spring tension???