primer goes off but is all

[kt]

petey has it right as usual. the black tapered end is actual black powder which ignites at a lower temp than the rest of the pellet. i wouldnt chance it either. there is suprising force in a 209 primer, if you ever just fire one off pointed at the ground it moves the leaves on the ground. i find it hard to imagine you have the breech plug that gunked, but one thing i have noticed is if you swab with something like borebutter on a patch it will plug up, but i have never ever had a 209 go offf without igniting the charge, and on that thought, should your charge not go bang, after some times i think the bullet should be pushed on once or twice as some say the force of a 209 can push the bullet on its own.
kt