There are several websites that illustrate Civil War muskets, if that is the period you are interested in.

http://www.angelfire.com/ny3/76thnysvol/civilwarguns.html

http://www.relicman.com/w0610.htm shows a musket and closeup of the parts.

Here is a parts list: http://www.relicman.com/w0610.htm

Hope this is of help.