There's not a ton written about this that I can find, but cracks are appearing in the US military's plan to replace the M4 with a heavier battle rifle designed to defeat body armor. Sig Sauer, which also holds contracts for the current generation pistol and LMG, won a contract last year to also provide the US military with a new rifle. This rifle is to be called the XM7. The civilian equivalent is the Sig Spear. Calling this thing an assault rifle is a bit of a stretch, as it is very heavy and uses heavy ammunition. It turns out that the rifle is failing to penetrate modern body armor without the use of tungsten bullets. Also its reliability is questionable.
there have to be parts that can be replaced by plastic. even if those parts are subject to heat, some thermoplastics are stable upwards of 300C. parts like magazines, the handrail, the stock (that one is probably already plastic). how is it this hard to design a gun thats better than one designed in the 80s? hell, maybe just have a barrel with an inner shell of titanium-steel alloy and an outer shell of any old steel