Angstadt Arms Jack-9 Pistol with Sharps Bros billet receiver set and Strike Industries components. In 1982, Colt introduced a straight blowback 9mm design for the M16 family designed by Max Atchisson and implimented by Henry Tatro in 1985. The design lacked the gas tube, had a magazine block, and used both stainless firing control group pins and a heavier buffer to accommodate the stress created by a straight blowback 9mm. The 2000's began an era of heavy accessories using standard forged receivers whereas the 2010's were the opposite. Sharps Bros began manufacturing milled receivers for AR15's in 2012 followed by their MB47 Kalashnikov milled receiver with integral AR15 buffer tube assembly under contract by Jim Fuller at Rifle Dynamics. When Angstadt Arms manufactured the UDP9, they started with milled receivers and reduced the overall profile from that of a rifle cartridge into a pistol cartridge cutting the receiver size in half and no longer requiring a magazine block. Recently Angstadt Arms teamed up with Sharps Bros to manufacture their billet receivers with pistol cartridge profile designs and utilizing Glock magazines. Strike Industries began in 2011 thinking outside the box manufacturing innovations that others had never implimented including modular forearms for AR15's and AK's and even a modular MP5. When the battle of the Keymod and M-LOK was going on, they said "Fuck it! Strike Industries accessories will universally use BOTH!" and introduced their LINK system. My absolute favorite of Strike Industries designs is their latchless charging handle. Everyone knows when your AR15 charging handle latch breaks, you're fucked. Strike Industries solved this problem utilizing a leaf spring that locks itself into the upper-receiver without a latch and is universally compatible with all standard AR15.