Only two of the firearms in my collection were ever sold by the federal government, a Model 1903 Springfield rifle I inherited from my father-in-law and an M1 carbine that I’ve owed for decades. Even though there were at least two intervening owners between the government and me for both rifles, I suppose it would be technically possible for the government to say it wanted to buy them back, but they’re not for sale.
Now, about my AR15 … Mine is a Colt Sporter in 7.62x39mm. That’s an odd chambering for an AR15, but the cartridge is legal for deer in Maryland—the more common .223 Rem/5.56 NATO round isn’t—and it’s my preferred deer rifle for hunting in the woods. I didn’t buy it from the the government, and even if Colt were to make an offer, it’s not for sale.
BTW, the Springfield is an interesting collector’s item. It was produced just after World War One, so it was one of the first made using the improved heat treating process for the receiver. It also has the cutout for a Pedersen Device.