I have a Stevens 200 (savage 110 copy) in .308 Win. I am using virgin R-P brass and a new box of Winchester brand large rifle primers.

I have had this rifle for a few years and I have never had any problems with it not firing. I have probably shot around 100-150 rounds until it started acting up. On my last batch of reloads, I had 2 or three out of twenty that wouldn't fire and I thought maybe they were bad primers, so I got rid of all those primers and started again. I have heard that it could be the headspacing on my reloads, but I have been using one of the case gauge things on the cases and they fall just where they are supposed to fall both after sizing and after loading. I also read that it could be "gunk" in the bolt, so I took the bolt completely apart and cleaned it out. It did have some brown gunk that i needed to scrub out of it and now it is all shinny clean; I lubed it up with a light coat of a "tactical" type gun oil. I put it all back together and took it to the range today, and now I couldn't get it to fire any of the 4 rounds i tried.

So, what is going on? Any idea what I need to do next? The gun is only about 6 years old and only about 100 rounds fired through it, so I don't think the fire pin could be weak yet!
Ideas?