Experience the ballistic performance of the iconic FN P90 in the familiar AR-15 platform with a 5.7x28 upper receiver from Classic Firearms. Whether you're looking for a rifle or pistol upper, we've got just what you need to complete your dedicated AR57 build for sale.

This upper receiver is chambered in 5.7x28mm and features a steel 16" barrel with 1:8.5" twist and a 1/2x28 thread pattern. This AR57 Upper is constructed with a steel barrel, muzzle brake, …

5.7x28 AR Uppers are chambered in the small yet potent round. Now available in the AR 5.7 rifle platform with proprietary magazines.

Convert your AR-15 type rifle to shoot the same 5.7x28 ammo as the legendary FN P-90 PDW! This AR57 Upper is constructed with a steel barrel, muzzle brake, bolt carrier group, buffer, and screws, all built into an alloy monobloc receiver.

Convert your AR-15 type pistol to shoot the same 5.7x28 ammo as the legendary FN P-90 PDW! This AR57 Upper is constructed with a steel barrel, muzzle brake, bolt carrier group, buffer, and screws, all built into an alloy monobloc receiver.

The AR57 Upper Receiver Assembly converts an AR-15 to shoot 5.7x28 FN ammunition. The unique upper design loads on top and accepts FN PS90 magazine (not included) and ejects downward through the AR-15 magwell. This upper is precision machined from a one piece aluminum forging.

Elevate your firearm performance with the impeccable engineering of this 5.7x28mm Complete Upper. This cutting-edge AR57 Upper seamlessly integrates into any standard lower, ensuring you experience smooth, hassle-free installation and use.

32 Round Magazines Available Here! Shop 16" 5.7x28 AR-15 Complete Upper at KM Tactical with the best price and fast shipping. Buy today for great deals!