Forgotten Weapons gets to try the AR57 rifle, an AR rifle that fires 5.7mm round fed with the P90 magazine. An airsoft version is made by Echo1 USA Airsoft... "The AR-57 is a system developed by Rhineland Arms in the early 2000s which uses the FN P90 magazine (and its 5.7x28mm cartridge) in an AR upper. The magazine mounts on top of the barrel, and it ejects downward through what would normally be the AR magazine well. Any standard AR lower can be used, although the company (AR57; a separate firm spun off for this product) sold complete guns using OEM receivers form Aero Precision.

The uppers were made in three barrel lengths, and I have here an example of a first generation full-length rifle and a second generation SBR with a 6.25" barrel and a GSL Technology suppressor nested inside the handguard.

Further thanks to Battlestar Gatlactica for the loan of the 1st generation rifle!"