BudsGunShop.com - ATI OMNIHYBRED MAXX PSTL 5.56 vs ATI GOMNIPH7QA55

The cheaper one is a 5.56 chamber, the more expensive model has a wylde chamber that accepts .223 and 5.56.
I would buy the cheaper one and not look back.

Based on the Omni Hybrid reinforced polymer lower from American Tactical, this is a great example of an AR-platform handgun. Perfect for plinking, personal defense, use as a truck gun or tactical applications, this pistol features a 7.5" barrel with 1:9" twist, covered with a 7" free-floating quad rail hand guard, giving you plenty of real estate for back up iron sights, lights, lasers and other accessories.
Specifications and Features:
5.56 NATO (accepts .223 Remington)
Gas operated semi automatic
7.5" barrel
1:9" twist
30 rounds capacity (ships with Magpul PMAG)
Reinforced polymer lower receiver
Pistol length gas system
7" free floating quad rail hand guard
Flash hider
Weight 4.75 lbs
Black
The American Tactical Imports Omni Maxx AR-15 Pistol is a compact, lightweight semi auto firearm that is ideally suited to the personal defense weapon (PDW) role for use in and around vehicles and other tight quarters. It has a polymer upper receiver and a hybrid metal reinforced polymer lower, a 7.5" barrel and a quad-rail handguard. The pistol is supplied with no sights and is ready for your iron sights or optic of choice.
Specifications and Features:
American Tactical Imports ATIGOMXP556
5.56 NATO (also accepts .223 Remington)
Direct impingement gas operated semi automatic
7.5" barrel
Polymer upper receiver
Hybrid metal reinforced polymer lower receiver
30 rounds capacity
Quad rail forend
Weight 76 oz
Black