Mossberg 590

  Great shotgun, have another project  coming. 20 inch barrel, Tacstar side saddle. 
Bayonet & Mount lugs factory. 
Sling Swivels. 
Heat-Shield. 

Extras Cost$ Stock sleeve. 
Flashlight & Mount. 

Also, I did buy and add the second swing swivel mount screw. 

What I mean is, the 590 comes with 1 swing swivel screw. 

So when you mount a bayonet, there is a second tapped hole on the bayonet lug backside, to mount a sling, as your sling can’t be used as the bayonet is there in front. 

Leaving a screw hole, at the top of the magazine, that allows for debris and water to get in. Mine is covered with that extra purchased screw.