The following is from a military review of the M1014 (M4). It indicates the weapon is designed to hold 6- 3 inch or 7- 2.75 inch shells in the magazine tube. Some persons have commented on being able to insert 7- 2.75 inch shells. See the following:
The characteristics of the M1014 Combat Shotgun
Manufacturer: Benelli U.S.A. Corporation.
Caliber: 12 gauge, accepts 23/4" and 3" standard and magnum loads.
Length: 39.8" w/stock extended, 34.9" collapsed.
Weight: 8.44 lbs. empty.
Safety: Ambidextrous manual cross bolt.
Magazine Capacity: Six 3" shells seven 23/4", plus one chambered round can be unloaded without cycling through the action.
Trigger Pull: 5.5 to 7.28 lbs.
Buttstock: Modular telescopic with removable pistol grip.
Sights: Adjustable aperture rear and fixed post front, radius 23.7"
Maximum Effective Range: 40 yards with 00 buckshot and in excess of 100 yards with the rifled slug.
NINE in mine.
7 in the magazine tube
1 on the lifter
1 on the chamber