Part of it definitely depends on your interpretation of the second 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.

I suppose there's an argument to what a "well regulated militia" is, to some that could suggest that the available weapons should reflect what the military uses, which to many others would seem a gross overstatement.

Realistically, I don't know where we should sit on the slope. I think an equally important part of the conversation is discussing what the goals of the restrictions on gun sales are, and discussing the motivation for gun ownership (which correlates with gun violence). Recent trends in the US are positive, although public opinion is murky on gun control. I understand that in our society, there is an argument that public opinion on matters such as this deserve to be reflected in the law - that if people want to own pistols or have greater access to weapons they should have those rights - but I also don't know if I trust popular opinion on these matters, especially with how public opinion is influenced by the media's portrayal of gun violence.

For myself I see no benefit towards owning a gun. I would hope that less people in the US wanted guns, but I don't think we ought to address that through gun control laws - I don't actually know how convince people that they don't need to own them.

This doesn't really address your question, which I think is a really good question! I suppose I believe in general that gun ownership should allow for personal protection and sport, but not beyond that. Limits on magazine size, bullet type, etc. seem to make sense to me, but I don't actually know enough about guns to suggest with confidence what changes would be best. But I suppose if I had to draw a line, rhetorically that is where I would - in terms of legislation it would require somebody with expertise to figure out.