Quote Originally Posted by tenthumbs View Post
I was reading something and it said that whatever country wouldn't allow AR's in if the upper wasn't the same caliber as the one on the lower. I'm probably not stating this properly,but I have three 6.5Grendel uppers on regular AR lowers. I got to wondering if some states might dislike this setup.
In the US it is not an issue. An upper is just an acessory for the firearm (the lower). In other countries, they can make their own rules. If exporting to other countries, see ATF guidelines regarding exporting. If just travelling with your AR, check with host nation's customs agents as their websites could give you the best and most up to date info.