If you are looking for a .410, I would suggest the Mossberg 500. I bought one a couple of years ago for shooting pigeons in the shed.
Its a sweet little gun for 300 bucks. I tried to find an H and R single shot, but they are discontinued.
When my buddy wants to challenge me to a round of clays he takes my Benelli and leaves me with my .410. Its still not enough handicap! He will clean my clock with a rifle, but I whip him with a shotgun.
I would not change barrels on that Mini 14. You can shoot .223 so cheap now its ridiculous. I dont bother reloading for .223 at all. I cant make them as cheaply.
I have some AR parts that I need to do something with. My buddy bought me a Spikes Tactical lower and a fancy new hand guard. The hand guard is cool as it does not use a nut that has to be aligned with the gas tube. It has a nut that is small so the tube goes above it, and then the hand guard is located with allen screws at an angle.
I need an upper, all the parts for the lower and upper, plus a light 24 inch barrel. I was going to chamber it in 22x6.8, my gunsmith really likes that one. But .223 is so cheap to shoot.