All the more reason not to assume they would be okay with it. They didn't have to face this situation,
This is just like the argument liberals make against the Second Amendment. The Founders only knew single-shot muskets--they wouldn't have been okay with people owning assault rifles! Do you support that argument?
Your statement is so fuzzy I can see three different possibilities in it.
1. You are asserting that I am projecting my own assumptions.
2. You are asserting that you are against the notion that founders would support assault weapons.
3. You are in Favor of the notion that the founders would have supported assault weapons.
If it is number one, the assumptions are axiomatic and based on the presumption that the founders were not complete idiots, as they would have to be to allow automatic citizenship to anyone who can sneak across our border against our wishes.
If it is number two, then I would argue the founders were in favor of the citizenry being able to defend themselves, their state, and their sister states from attack by a tyrannical government, and would therefore understand the weapons to be the latest Military grade killing tools.
If it is number three, then I agree with you.