A post from 2003 has the following guns of the battery for different dates, but whoever posted it didn't put the source so I don't know the accuracy (unfortunately it doesn't address the question about the siege guns either.

armed with five 6-lb Smoothbores and one 3.3 inch Rifle between 1/1/1863 and 11/28/1863 - armed with two 6-lb Smoothbores, one 3.3-inch Rifle and one 12-lb Howitzer on 5/1/1864

Link to the post: http://history-sites.com/cgi-bin/bbs53x/arcwmb/arch_config.pl?noframes;read=3207