Generally an SBR is considered no different than a riffle under most state laws. With this in mind, you have to look at your CWP statutes to see how a weapon or firearm is defined for purposes of the statute.
In Florida, the statute that deals with Concealed weapons and firearms defines what can be carried (Florida Statute 790.06 –License to carry concealed weapon or firearm) which states:
(1) The Department of Agriculture and Consumer Services is authorized to issue licenses to carry concealed weapons or concealed firearms to persons qualified as provided in this section. Each such license must bear a color photograph of the licensee. For the purposes of this section, concealed weapons or concealed firearms are defined as a handgun, electronic weapon or device, tear gas gun, knife, or billie, but the term does not include a machine gun as defined in s. 790.001(9).
This means that an SBR cannot be carried concealed in Florida. In addition, a Machine Gun Pistol would not be able to be carried concealed with a Florida CWP.