Yes semi autos are legal in MO, I hope your wanting to use the 10/22 for small game,,lol.. For deer any centerfire cartridge is legal by the state laws,, some think it should be limited to .24 caliber, but so far it isnt, if Im not mistaken the mini 14 is a .223? It is legal, but you can only have a 10 round clip. Any centerfire cartridge and a rifle holding no more than 11 rounds including the chamber, is legal, along with slugs, but no buckshot for deer. I think the deer hunting in Mo is good, but weve been managing our farm for about 10 years now, so we have some good bucks on it, and the bordering landowner on two sides of our property doesnt hunt or allow hunting,, he state does need to put the antler restrictions state wide, but have several counties which are restricted to 4 points on one side, and I know there are come counties near KC that are restricted. Id say come try it out, you may like it, and you can just buy a tag over the counter, it dont get much easier. Good luck if you go.