If you're shooting pellets instead of loose powder it does not surprise me you are having misfires. #11 caps are not recommend for pellets. They just do not have enough fire most the time to give consistant ignition. If you are not preparing the rifle for shooting then misfires can happen. If you are doing your part and using loose powder, that rifle should and will go off.

Before you load... Take a patch and put some isopropyl 91% alcohol on it and then swab the barrel. Now run two dry patches through the barrel to make sure it is bone dry. Put a new patch on that cleaning jag, push it to the bottom of the breech on top of the breech plug and pop a cap. Pull that patch and look at it. It should show burn marks. If not, pop another cap through the breech. Now push another patch down there and do it all over again. Pull that patch and it will show burn marks. If it does not, then pull your breech plug. Something is plugged there.

Once you got fire coming through the hole, and loose powder, that rifle will fire as well as it would with a 209 primer. #11 primers are a lot more water proof then people give them credit for. On my inlines, I prefer the #11 cap. Less crud build up and I carry around a straight line capper for the day of hunting. Not that I have anything against 209 primers.

Like I said, if you're shooting pellets.. that is your problem. If it is loose powder and a good quality cap like a CCI MAGNUM or a 1075 RWS you will fire that gun.