I came up with "much" less than your figure......

https://www.boisestatepublicradio.o...legal-it-takes-lot-get-one-630000-us#stream/0
With the commonly accepted figure of some 300 million firearms in the us I came up with some .0021%. That's roughtly 2 one thousands of one percent. Even if you factor in illegal fully automatic firarms, and I don't know where your figures are from, I'd seriously doubt you'd get anywhere near 1% much less the 4% of all us firearms in private hands.

Okay let's use the numbers in the linked article. "According to the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF), as of 2017, there were 630,000 machine guns in the U.S. That, however, is a fraction of the roughly 400 million guns in America."

630,000/400,000,000=.001575 X 100 = .1575%

Quite a bit higher than the .0021% you came up with. It appears you forgot a step in your calculations of of percentages of machine guns to total firearms.

BUT, the question you asked was:

Question, how many here in the us facing a shtf are going to have "aimed controlled automatic fire" as an option percentage wise?

My answer was using the number of people in the US about 327,000,000 (which includes all ages)and the number of available machine guns. Let's, again conservatively, 10% of the population is too young to participate in repelling an invasion that leaves 32,700,000 (about half of which are female but that is a debate for another time). Accepting the 630,000 number, which I believe is low, 630,000/32,700,000 = .019266 X100 = 1.9266% of the population potentially capable of responding with a firearm could have a "machine gun". If you want to be sexist and say females would not be there that takes it up to over 3.8%

BTW, Ratio vs percentage:

https://sciencing.com/calculate-ratios-percentages-8098194.html
"Convert the Decimal to a Percentage

Multiply the result from Step 2 by 100 to convert it into a percentage. Continuing the example, you have:

0.7333 × 100 = 73.33 percent"