lmost nothing about the confederate constitution sought to conserve the oringal U.S. constitution.

And that's where you are wrong my friend. The Confederate Constitution actually copy-pasted the US constitution almost in its entirety. This is partly why the Montgomery Convention managed to produce it so quickly, because they basically took the US Constitution and modified it slightly. Some of the changes were important and revealing of Confederate goals and philosophy, the clearest one being that they did away with the euphemistic use of "person held to service or labour" and just called enslaved African Americans "negro slaves", adding several articles detailing how important slavery is and limiting the government's ability to interfere with it even more (and take into account that the US government already was limited on what it could do against slavery).

For example, the Confederate Congress would have no power to limit slavery in any territories the Confederacy might acquire. The US Congress traditionally had that power, though one should note that Southerners often contested that it didn't and Chief Justice Taney agreed with them in the infamous Dred Scott decision. By making slavery legal everywhere, declaring that no "law denying or impairing the right of property in negro slaves shall be passed" and denying that Congress had any power to interfere with it, the Confederates were showing their commitment to slavery and their utter repudiation of the Republican Free Soil platform.

There were some more changes that weakened the Central government and the presidency, such as allowing the States to impeach federal officers that served within their borders or limiting the president to just one six year term without reelection. The "general welfare" clause of the preamble was omitted and states rights emphasized instead, and the government was prohibited from laying tariffs to protect industry or give aid to internal improvements, two mostly Whiggish Republican issues the majority Democratic South had opposed in the antebellum. Curiously enough, the president was also given a line-item veto for appropriations. The amendment process is also dramatically changed. Whereas in the US an amendment requires 2/3rds of the House and the Senate, or 2/3rds of the state legislatures to call a convention to propose amendments, in the Confederacy the Congress would play no part in the amendment process. Instead, three states would have to form conventions, and then those three conventions would call for a general convention that could propose amendments. Instead of needing 3/4ths of the states to ratify, they would only need 2/3rds.

Aside from these changes, the Confederate Constitution was "copied verbatim" from the US Constitution. That includes the 2nd amendment, which in the Confederate Constitution is number 13, section 9, Article I. It's a literal copy paste of the original text: "A well-regulated militia being necessary to the security of a free State, the right of the people to keep and bear arms shall not be infringed." If this article does indeed mean that having guns is a right of the American people (and there is a lot of discussion, both historical and politic about that), then the Confederate constitution recognizes it as a right too. This is the only article of both constitutions that deals with the right to keep and bear arms, unless you were thinking of a different article.

But, yeah, to summarize. The Confederacy actually conserved almost everything in the original US Constitution and did not "destroy" the 2nd amendment. The right to bear arms was retained and given to all Confederates, except the enslaved, obviously. It was still a right.