I previously reported that on the new Mossberg 590 SPX. It appears Mossberg also have a “regular” 500 SPX.

The SPX features:
* 18.5″ ported barrel (the holes are in just behind the front sight)
* Picatinny rail
* LPA Ghost sight
* “M16 style” front sight
* Adjustable stock.
* 6 round magazine
This shotgun really seems to be crying out for an 8 round magazine upgrade.
The more expensive 590 SPX has a nine round magazine, bayonet lug and Ontario M9 Bayonet.
R&R Arms has it listed for $494.44 but have none in stock, I am not sure if Mossberg has yet shipped any.
UPDATE: There is also a 930 semi-automatic version of the SPX.

The Mossberg 903 SPX autoloader has the same features as 500 and 590 SPX except it has a 8 round magazine.
In 2009 Mossberg will be selling a range of Mossberg 590A shotguns and accessories to the general public. The 590A is sturdier than the 500/590 and is the model generally sold to law enforcement and military. The 590 has a heavy barrel, metal trigger guard, metal safety and bayonet lug.

Mossberg 590A, 6 round magazine, adjustable stock
A range of models will be available:
590A1 Adjustable – 6 Shot – 12 Gauge
• Barrel Length: 18.5”
• Sights: 3-Dot
• Choke: Cylinder Bore
• Overall Length: 36 1/8”
• LOP: 10 ½”- 14 ¼”
• Finish: Parkerized
• Stock: Black Syn, with 6-position, aluminum tube stock
• Weight: 7-½ lbs
590A1 – 6 Shot – 12 Gauge
• Barrel Length: 18.5”
• Sights: 3-Dot/Bead/Ghost Ring – depending upon model
• Choke: Cylinder Bore
• Overall Length: 39.5”
• LOP: 13-7/8”
• Finish: Parkerized
• Stock: Synthetic/Synth. Speedfeed – depending upon model
• Weight: 7-1/4 lbs.
590A1 COMPACT – 6 Shot – 12 Gauge
• Barrel Length: 18.5”
• Sights: Ghost Ring
• Choke: Cylinder Bore
• Overall Length: 38-5/8””
• LOP: 13”
• Finish: Parkerized
• Stock: Black (wood stock/synthetic forend)
• Weight: 7-1/4lbs
590A1 MARINER® – 6 Shot – 12 Gauge
• Barrel Length: 18.5”
• Sights: Bead
• Choke: Cylinder Bore
• Overall Length: 39.5”
• LOP: 13-7/8”
• Finish: Marinecote
• Stock: Black Synthetic
• Weight: 6-3/4 lbs
590A1 SPX – 9 Shot – 12 Gauge
• Barrel Length: 20”
• Sights: Ghost Ring
• Choke: Cylinder Bore
• Overall Length: 41”
• LOP: 13-7/8”
• Finish: Parkerized
• Stock: Black Synthetic

Mossberg SPX
590A1 – 9 Shot – 12 Gauge
• Barrel Length: 20”
• Sights: Ghost Ring
• Choke: Cylinder Bore
• Overall Length: 41”
• LOP: 13-7/8”
• Finish: Parkerized
• Stock: Synthetic/Synth. Speedfeed/Aluminum tube Adj. – depending upon model
• Weight: 7-1/4 lbs
The full press release is at AmmoLand.