As a primer, Maxim's firearms generally include options for chamberings in three calibers – 5.56 NATO, 7.62x39, .300 BLK – with stock/brace options that make them either a pistol or short-barreled rifle (NFA rules apply). They generally also come in arid or black, with urban grey now coming online as well.
These guns are made from military-grade materials (17-4 Stainless Steel, 7075 and 6061 Aluminum) and include the company's low-flash Hate Brake muzzle booster, which aids in reliability. Top rails, Maxim's compact buffer carrier system, and a free-floating slotted handguard are also standard.
Where the fundamental differences between models come are in barrel/overall lengths and receiver construction. Let's get in to that.
What Maxim bills as the king of the short game, the company's big splash was the PDX. Arising from the SOCOM Personal Defense Weapon solicitation, it is a hyper-compact design that uses a 5.5-inch barrel, which gives it an overall length of 18.75 inches. An ALG defense combat trigger and dependable operating system, which includes an integrated BCG with an interchangeable buffer weight, make it reliable while still being a direct impingement system. Maxim even offers an upper build kit so you can use your own lower to craft your own.