18 USC 922(a)It shall be unlawful—
(7) for any person to manufacture or import armor piercing ammunition, unless—
(A) the manufacture of such ammunition is for the use of the United States, any department or agency of the United States, any State, or any department, agency, or political subdivision of a State;
(B) the manufacture of such ammunition is for the purpose of exportation; or
(C) the manufacture or importation of such ammunition is for the purpose of testing or experimentation and has been authorized by the Attorney General;
(8) for any manufacturer or importer to sell or deliver armor piercing ammunition, unless such sale or delivery—
(A) is for the use of the United States, any department or agency of the United States, any State, or any department, agency, or political subdivision of a State;
(B) is for the purpose of exportation; or
(C) is for the purpose of testing or experimentation and has been authorized by the Attorney General; [1]

也就是说，美国法律规定只有用来给美军和政府部门使用或者出口的穿甲弹生产和制造或者进口才是合法的，民间不能使用。给民间使用穿甲弹的生产和进口是非法的。

这是和美国禁止民间使用自动步枪一样，防止民间暴力反抗政府规定的。

和你在正在讨论的中国95步枪全面使用钢芯弹的先进性毫无关系