Hey all. I've been kicking around the idea of building/ buying a short barreled gun to be nothing more than a truck gun. It will be used for mostly varmints and occasionally used for target and such. Wanting it to be a detachable mag for ease of loading/ unloading. I'm just curious what you guys would recommend? I've been kinda thinking 223, 6mm/223, 221, or maybe a 300/221 for someting different. Thanks!