What powder are you using? I use CCI #11's and haven't had any issues (using goex), except for when I did what was just mentioned...swabbed between shots and pushed crud into the flame channel. I've never tried pyrodex or 777, but have heard that the magnum caps are best for igniting them (except 209's of course, illegal to hunt with in Idaho), or musket caps like mentioned. I would think if the caps are going off then they aren't the problem. Trying a tin of magnum #11's won't necessary show that the non mags are to fault, as they are hotter. A new tin of non mags would tell you though. When you said you shot it at camp two years ago, did you use the rest of the mags and then this year it was the non mags? The caps do seem to be the common denominator if your using the same powder and it hasn't gotten any moisture to it, but if you're using pyrodex or 777 then I'd bet it has to have the hotter mag caps to ignite it reliably.