3 inch chamber so up to 3 inche shells dow to 2 3/4in. Can use about anything from target loads to slugs an buckshot. I reccomend for best results, using high brass shells. Good luck

Drake, it has a 3 inch Chamber and will fire 3 inch or shorter 2 3/4 inch shells Sir. Just stay away from the light loads and reduced recoil loads in slugs or buckshot and you are golden. I highly advise a 50 to 75 round break-in with full powered loads and then a thorough cleaning/lube. Cheers and stay safe!

the only way to know for sure is to try different ammo The most common 12 gauge target loads contain 1 ounce of shot at a muzzle velocity between 1180-1290 fps, or 1 1/8 ounce of shot at 1145-1200 fps. Depending on the individual gun (after breakin) it may or may not work

Drake, any high velocity (at least 1300 fps) shell, either 3" or 2 3/4, should work in this gun. Stay away from low brass. The following is taken from the owner's manual---
As with all gas-operated shotguns, a short "break-in" period of a box or two shells for reliable operation is required. It is recommended that loads of 1 oz to 1 1/8 oz and 1250-1350 fps be used with the low velocity piston that came pre-installed in the gun for the "break-in" period. At any point, do not use loads above the above-listed weight or velocity without installing the HV marked piston first.
Shotgun ammunition has an extremely wide range of projectile styles, weights, and velocities. Gas-operated shotguns are only intended to run on STANDARD weight and velocity ammunition. Most ammunition labeled "low recoil" does not have enough pressure to operate semi-auto shotguns. There are also many styles of ammunition that are beyond the factory recommendations for weight or velocity. 1.5 oz maximum or 1500 feet per second is the maximum safe limit.

This shotgun has a 3" chamber and can shoot 2¾ or 3" shells
Full specs here
http://armelegant.com/product/magazine-fed/64-armelegant-ang-4.html
It will cycle all types of ammo but higher velocity shells are going to cycle the most reliable 1200 FPS or better.