Textualist, Historicist, Originalist, Functionalist, Prudential, Doctrinal, Naturalist, Equality...
Those are 8 different ways in which laws can be interpreted. Strict Textual is not always possible, or even prudent in some cases. When a framer has supplemental papers that underscore or explain their intent or meaning in a certain passage, that can be taken and used as well. Not all people, now or then, agreed on what all meanings of the words actually mean. While my reading of the papers written by the framers tells me that they did not intend for the Constitution to be a "living" document, they certainly did intend to impart some elements of a Naturalist interpretation. Understanding of the meaning of the words then and what the actual intent would be now is also imperative, and is included within the Historicist viewpoint.
IF, you are stone set on only a Textual reading, then realize that only flintlocks were available and those are the firearms they knew about, so...that supports the liberal interpretations.
I will take an Originalist over a Textualist
Originalists think that the best way to interpret the Constitution is to understand how the Framers intended the Constitution to be interpreted. Documents such as the writings of the framers, newspaper articles, Federalist Papers, and the notes of the Constitutional Convention need to be evaluated in this method.
Textualists believe that the only thing needed to interpret the Constitution is a literal reading of the words contained in the document. They do require an expert knowledge of the 18th century meaning of those words. But the Textualist does not use supporting documents to answer questions and provide context. This is one of the problems regarding the definition of Firearm and Militia with this method.