Thanks Jimro: you've hit it right on the head. I'll try that first, and see what happens. Right now the spring looks somewhat rusty and dark to me... As it is, when I do manage to cycle a round, the tip gets caught in the front of the breech, before the chamber. I noticed that the tips do get a bit mashed when I force things. So I'll try to install the block first and see if that helps. I've got a new synthetic stock and mag spring in the mail, so I should be right!