I have had several regrets in selling off firearms that I wish I would have held on to. One of my biggest regrets was selling a Russian Saiga rifle off because I couldn’t get anything but 5rd magazines for it, and then I found out that it was possible to legally alter the firearms so that it could take 30rd magazines. It was a very small gunsmithing alteration that would have been done in a few minutes. You just had to know that it could be done.
Another regret I had was selling off a Ruger 10/22 rifle because the gun wasn’t very accurate compared to my Marline bolt action rifles, but after taking several kids to the range, I found out that the children under 8yrs old had trouble with the length of the rifle stocks and something as small as the Ruger 10/22 would have worked since it had such a short LOP. If a gun isn’t junk, you may want to think about why you should hang on to it, because you may wish you did.