Yes it is the 12 ga 3 inch magnum Specifications and Features: Remington Model 870 Express Combo 81291 Pump Action Shotgun 12 gauge 26" Vent Rib Barrel 18.5" Home Defense Barrel 3" Chamber 4 Rounds Single Bead Sight Crossbolt Safety Synthetic Stock Matte Black Finish Length of Pull 14" Drop at Comb 1.5" Drop at Heel 2.5" Overall length 46.5"/38.5" Weight 7.5lbs

This shotgun has a 3" Magnum chamber. 3.5" would be a super magnum chamber and 2.5" a standard chamber.

The gun Steve P linked to is the 31/2 inch Super magnum 2 3/4 inch standard 3 inch magnum and 3 1/2 inch super magnum

Yes it is the 12 ga 3 inch magnum Specifications and Features:
Remington Model 870 Express Combo 81291
Pump Action Shotgun
12 gauge
26" Vent Rib Barrel
18.5" Home Defense Barrel
3" Chamber
4 Rounds
Single Bead Sight
Crossbolt Safety
Synthetic Stock
Matte Black Finish
Length of Pull 14"
Drop at Comb 1.5"
Drop at Heel 2.5"
Overall length 46.5"/38.5"
Weight 7.5lbs

Here is the magnum model -
budsgunshop.com/catalog/product_info.php/products_id/95100/Remington+870+Express+12+3.5+28+Rem-Choke+Mod+Wood

Hi John, No it isn't a magnum Specs - Specifications and Features:
Remington Model 870 Express Combo 81291
Pump Action Shotgun
12 gauge
26" Vent Rib Barrel
18.5" Home Defense Barrel
3" Chamber
4 Rounds
Single Bead Sight
Crossbolt Safety
Synthetic Stock
Matte Black Finish
Length of Pull 14"
Drop at Comb 1.5"
Drop at Heel 2.5"
Overall length 46.5"/38.5"
Weight 7.5lbs
Includes:
1 RemChoke Pattern Choke Tube: Modified