Have you had misfires due to light trigger hammer springs using 308 mil-surplus primers?

I've shot Wolf, Silver Bear, and Belgian 308 surplus just fine in my HK-91. In my DPMS 308 with Jewell match trigger, the primer strike seems a bit light. Approx 50% of the Silver Bear failed to fire (primer is dented deep). Approx 10% of the Wolf failed to fire. Approx 5% of the Belgian 308 NATO failed to fire.

How can I increase the trigger hammer spring on a Jewell trigger?

Thanks, Charlie.