Joe, I had the same experience. Don't remember which rifle I put the 5/16" WL in, but I think it was an Issac Haines .40, don't remember which lock. I had a drilled flash hole, about .080", very reliable but Swiss 3F would run out. So I installed the WL. Had about 25 flashes in the pan with the first 50 shots. The flash hole is about .055, and the liner does not come with instructions. After I drilled it out to about .070, it worked reliably. Just installed a 3/8" on a .58 flintlock Hawken I built, Manton and Ashmore lock, and it gave some flashes in the pan with Goex 3F and 2F and Swiss 1 1/2. Chronographed a load and then opened it up from .055 to .0625. Lost about 20 fps velocity, but only an occaisonal FIP, usually with Swiss 1 1/2. About .070 to .078 would be a better hole, from my experience.