Do the musket capsgo by the name of a magnum #11 cap?
No, #11 caps and #11 magnum caps are the same physical size. The magnum is "hotter".
The musket nipple is physically larger than an #11 nipple. In the picture below, the #11 is on the far right and the musket is second from the right.
Here's a picture of musket caps.
Click here for a picture of #11 caps.
http://www.cabelas.com/cabelas/en/common/product/popupzoom.jsp?company=cabelas&image=s7_210243_ imageset_01&inStockColor=1111&displayName= CCI No. 11 Percussion Caps&tProdID=0006579210243a