LocalBoy,
I wanted to see the problem again before disturbing things. So right now the sporter is sitting with the safety on to try and replicate the first incident. In a day or so I will do it again, with an empty chamber this time. If it does not repeat the fault I will start taking it apart  for analysis.
Just to be clear the pencil was stuck in the hole afterwards to show it up. Did not try spinning the pencil to see if the hat channels in the wall would act as a sharpener. Now you have given me a reason not plug the hole. :-)

Some days I am just slow. I finally caught on the question:

What load were you using behind that Pencil? Was it a #2 Ticonderoga, Eberhard Faber, Bostonian, or some Vietnamese Crap?
(Sorry, but, You know this question will be coming from 'Madsenshooter' or that little Ohio guy in Africa)!

Pencil was powered by the little finger with miniscule effort. :-) Not sure if I found the bottom of the hole, did not do any probing there. The cinder blocks under the window had the cores filled with concrete, seems like the 200 grain traveling at close to 2300FPS should have penetrated deeper. I doubt the pencil is touching the slug. Pencil was made in the USA, I bought a couple cases 30 years ago so as to not have to put up with foreign junk, still have about half of them.