Detachable mags. Right now there is only one rifle that I know about that has been given the okay by the atf to be for sale. The government doesn't want you to have a battle rifle that has detachable mags.
Accounding the the ATF's list there are several
Czechoslovakian, model 1952 and 1952/57, 7.62 x 45mm and 7.62 x 39mm cal., semiautomatic rifles.
Egyptian Raschid, semiautomatic rifle, cal. 7.62 x 39mm, original Egyptian military production.
Egyptian, Hakim (Ljungman) 7.92mm semiautomatic rifle as mfd. in Egypt.
Fabrique Nationale, model SAFN49 semiautomatic rifles, any caliber.
FN F.A.L. G and GL series, semiautomatic rifles, imported by Browning Arms Company, Arnold, MO from 1959 to 1963
French Military Rifle Model 1949/56, in 7.62 x 51mm (NATO) cal. French, model 1949, cal. 7.5mm, semiauto. rifle (Fusil Mle. 1949 (MAS) 7.5mm).
Russian (U.S.S.R.), Tokarev, semiautomatic rifle, model 1940 (SVT40), cal. 7.62 x 54R, of Soviet manufacture.
Russian (U.S.S.R.), Dragunov, semiautomatic rifle, model SVD, cal. 7.62 x 54R, of Soviet manufacture, Soviet military issue only.
U.S., Rifle, cal. .30 M1, original military issue only, produced prior to 1956.