There is no legal use of a gun that requires a gun capable of holding more than 6 rounds.

Asserting a negative - bold strategy. I'd be interested in seeing your support for such a position.

I frequently legally use standard capacity magazines at the shooting range, though, so you may have a hard time here.

More than 90% of self defense situations end with only 2-3 shots being fired. Long, drawn out gun fights with both sides firing 20-30 rounds simply don’t happen in self defense situations. It’s just a fiction from movies.

Is this one of those Works Cited: Crack Pipe moments?

What high capacity firearms do allow is criminals to maximize the damage they do in a short period of time.

Ah - so you only care about mass shootings, the vast minority of firearm violence let alone homicide.

Every constitutional right has limits.

Generally, I would be inclined to say yes, but things become more tricky when the constitutional right in question specifically states "Shall not be infringed". That being said, the limits in question could certainly lie within the definion of "Arms", and "bear".

There is no legal use of a gun that requires a gun capable of holding more than 6 rounds. More than 90% of self defense situations end with only 2-3 shots being fired. Long, drawn out gun fights with both sides firing 20-30 rounds simply don’t happen in self defense situations. It’s just a fiction from movies. You certainly don’t need that many rounds to bring down a deer.

Don't forget the original intent of the 2nd Amendment (I encourage you to read the Federalist Papers, to hear it striaght from the source) was to ensure that the people have the capability to resist their own government. Without a populace who believes in it, and will defend it with force if need be, a constitution is no more than a piece of paper, and a dream. Pay close attention to the wording of the 2nd Amendment:

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.

As well as how it would interract with what was stated in the declaration of independence:

[...] We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty and the pursuit of Happiness.--That to secure these rights, Governments are instituted among Men, deriving their just powers from the consent of the governed, --That whenever any Form of Government becomes destructive of these ends, it is the Right of the People to alter or to abolish it, and to institute new Government, laying its foundation on such principles and organizing its powers in such form, as to them shall seem most likely to effect their Safety and Happiness. Prudence, indeed, will dictate that Governments long established should not be changed for light and transient causes; and accordingly all experience hath shewn, that mankind are more disposed to suffer, while evils are sufferable, than to right themselves by abolishing the forms to which they are accustomed. But when a long train of abuses and usurpations, pursuing invariably the same Object evinces a design to reduce them under absolute Despotism, it is their right, it is their duty, to throw off such Government, and to provide new Guards for their future security. [...]