Ar in .243
Im looking for a semiautomatic .243 on the ar platform but I have no clue where to look. Not really wanted to spending a bunch of money but just wondering where I can find one or where I could get the parts to build one would be even better. Can an ar 243 upper be put on a ar15 lower with little to no gun smithing? I would love to build a ar .243 to save money.