Originally Posted by KeithinSC
I'd like to build my first AR someday, yeah my timing sucks. Just starting to start researching. It's been something on the list for 10 years.
I'd like a .308, can I use the same lower for that and get a .223 upper later on?
Or are the mags that different?
It depends on the lower but generally no, you can't use a .308 in a .223 lower. (some lowers do allow it though.) The magazines aren't not interchangeable. It's basically like comparing a long-action to a short-action.