When I finished shooting the other day, only fired 10 shots, I pulled the breach plug to clean the gun up and found a thick crunchy layer of whitish gray crud so thick that i couldn't see light through the pin hole. It did wipe right off with warm water but how much of that crud biulding is normal and will that biuld up start afecting the shooting?

Swab every 5-6 shots using large patches and bore brush. Keep the patches as dry as possible. If the breechplug flashhole was plugged, the ML would not fire.

You never mentioned your routine prior to firing your first shot. You never mentioned how you removed your storing oil - or what you swab with... including your patch size - which you use for swabbing .. ie....a bore brush or jag?

Something caused that powder to stick to the breechplug face. Odds are, you left the breechplug in and over-oiled the bore when storing your rifle. The oil ran down the bore wall & settled all over the breechplug face. I never install my breechplug until it's time to put the ML in the vehicle carrying case. That way, it stays dry as a bone.

Thanks for that. After further thought i think that that may be what happened I made sure the barrel was dry but didn't think to check the breach face.