Most all you need is money. Quite a bit of it. Or you can get a semiauto H&K PSG-1 in the same price range...without optics.
Sorry, you can't get ammo at WalMart.
You can't get a T-5000, either.
It is always money.
I have wanted an H&K PSG-1 since the 1980s. Even when I had a comfortable income they were just too expensive.