Mossberg Right short stock
Click for larger picture
(Right side with collapsed stock)
FACTS
 Brand  
 MakeMossberg
 Model500 (52440)
 Method of operation  
 Semi AutomaticPump
 Trigger1 Stage
 Feeding SystemTube 5+1
 Technical 
 Weight6.75 pounds
 Overall Length39.5"
Barrel Length18.55"
 ChokeCylinder Bore
 Functionality
 Bolt position when firedClosed
 Bolt upon last round firedClosed
 Magazine capacity5+1  (plus 5 on saddle with stock)
 Decocking or Dry fireDry Fire
 Field Stripping  
 Tools requiredNone
 Small parts retained or looseN/A
 Ammunition  
 Caliber12 Gauge 2-3/4" and 3"
Mossberg Left - long stock
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(Left side extended stock)
Opinions
 Method of operation  
 A pump 12 gauge shotgun with a smooth bore cylinder is the most effeicient mode of operation there is because the sound of it being readied is typically enough to discourage any threats.
 Functionality  
 PriceLow
 AvailabilityGood
 Modularity / AccessoriesOK
 AccuracyN/A
 ReliabilityVery Good
 Ease of field Stripping  
 Very easy its just a screw and then everything pulls right out.
 Ergonomics  
 Left or right hands can work the controls and it does have a pistol grip with an adjustable stock.  The controls are not changeable and the shells will always eject off the right side so not great for lefties. The sling under the pump ensures it wont slip off your hand.  The side saddle shell holder is also very nice but it would need to be relocated if shooting left handed.
 Sighting System (Optics)  
 It has a bead on the front and I would prefer ghost rings but they required gunsmithing which is a let down.  However a little brass bead is more than enough of an aiming device for a 12 guage.
 Ammunition  
 PriceNormal
 AvailabilityEvery where
 PunchKnown stopping power
 Links  
 http://www.mossberg.com/
 http://en.wikipedia.org/wiki/Mossberg_500
 http://www.remingtonle.com/ammo/ss_rrb.htm
Mossberg Right - long stock
Click for larger picture
(right side extended stock)

 My ramblings (Over all feelings; Why this Gun; is it worth it):

 Everyone should own a shotgun and if you can get a tactical one then your even better off. The shorter barrel gives you better portability but cuts down on overall firepower; which is compensated by the 5 round side saddle.  The adjustable stock, pistol grip, heat shield and pump sling add to the usability and ruggedness.  Everyone expected me to get a Benelli M4 12 gauge but for the price I had to go for the Mossberg pump and I am rather glad that I did.

Mossberg left short stock
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(left side with collapsed stock)

12 gauge 00buck 1 shot
Click for larger picture (1 shot with 00buck)

12 guage 00buck 5 shots
Click for larger picture(5 shots 00buck)