I don’t know if you know this but even the founding fathers who owned slaves didn’t believe in slavery.
Thomas Jefferson had in the Declaration of Independence the freeing of all slaves but ben Franklin told him no because NC SC and GA would never sign on.
This is really tangental to the subject at hand; but yes, I am aware of this. Technically, the account you give is not, strictly speaking, accurate (Jefferson was trying to abolish the slave trade, not slavery itself); but this is still an important point that ought to be remembered in any discussion of slavery's role in American history... which this is not.
Okay if the founding fathers believed in gun control then why didn’t they ban some of the most powerful guns then?
What? That is not my point at all. Please read my post again.
Times were different then
Exactly! And it is for precisely this reason that we should not project 21st Century political views onto deceased historical figures based on something they said or did 200 years ago: "times were different then," and to pretend as if we know where the Founders would stand on gun control, or immigration, or gay marriage had they lived to see the present day is intellectually unsound.