The alt right just makes up numbers.
There are only 16.2 million veterans total in the USA, and many do not own guns. Full auto weapons are very rare in the USA, they have to have been made before 1986. Semi-auto are more common, but a surprising number of them are owned by people who own many of them. That reduces the number that are owned by everyone else.
There is a reason that combat soldiers generally do not carry handguns. They are not optimized for warfare. Most of those semi-auto guns are handguns. I would not want to take on a M-16 with a Glock 26; especially if the soldier carrying the M-16 has modern body armor. I would much prefer a hunting rifle with some range.
That is what the Ukrainians used to kill so many Russian generals at the beginning of the Russian invasion.