I've filled up my Daystate Huntsman Classic, only to find it won't cock. After shaking the action vigorously, there's no sign of pellet debris.

My plan was to strip the action to find the problem; but how far can one strip with a full cylinder? (1st question)

It'll be ok to deal with the AT I thought: 2 domed head screw tops without slots.

I thought I'd drill 'em deep enough to punch a hardened posidrive bit into them. (A method I've used successfully before.) They seemed very hard tho' & then, (imagine my surprise) they started free wheeling round with the drill bit.

In reverse tho' they would'nt unscrew. They're recessed quite deep so can't grab em with tweezers. They won't fall out. I think they're non ferrous, a powerful magnet won't pull 'em out. What to try next? (2nd question)

Advice & suggestions most gratefully received.