I appreciate the replies. I looked in the rifle boxes and found plastic bags....with #11 nipples in them....(duh) lol. So I put them on the rifles and we went shooting. I fired around 10 and had 2 mis-fires (my son had none). Both times the #11 cap was half smashed but didn't go off, but ignited both times after re-cocking. (dynamit Nobles)
Anything I can do about that?
yes you probably can... the Nobles are metric instead being a true #11 they are 10.75 so they do fit a bit tighter. As the nipple gets dirty it thickens so it makes it more difficult for the tight nipple to be pushed down by the hammer. Probably if you were to keep the nipple stack clean after multiple shots every thing would work fine. I usually just wipe it with a damp Windex patch. This for me is only a real problem at the range - hunting not a problem.
Another thing that I have seen that causes the problem is if the cap is not place squarely on the nipple post - if it is canted off a bit it will often fail to fire the first time until the hammer squares it up.
The one good thing is if the nipple is placed on correctly and tight - it becomes nearly and for all intents - water proof.
Using a CCI Mag #11 you probably would never have a problem.