There are also #11 percussion caps. Some of my revolvers prefer 10's some prefer 11's. Musket caps are very large comparatively, but now are available with wings and without.

Make sure your nipple isn't clogged. A nipple pick is usually built in the "T" style wrenches. A straightened out paper clip will do in a pinch, Just avoid anything a magnet can pick up as it could spark and be more interesting than you bargained for!

Ivan