two things I have been thinking about are why is the symbol Spades found on some AR15? Actually I have only seen Spades symbol in tactical environment, why is it? Does it stand for something in the tactical environment?

The second thing is I have seen rifles with RDS coupled with a front iron sight without any iron sight at the rear end. How can BUIS be used when there is only one in the front? Am I missing something?

Forge mark & the RDS is being used as the primary sight-not the front sight.

Who uses the Spades symbol as a forge mark?

when you've seen the spade has it been on the upper or lower? i thought forge mark too, but i've also seen the spade engraved on lower receivers and i'm not sure of who uses the spade as their mark. the spade does have a bit of a history in war. i won't go into it for brevity, but just google 'spade symbol in war'.

Are you talking about the Cerro "keyhole" forge mark?




Cerro Forge is one of many companies producing raw forgings to be machined by the manufacturers that finish receivers.  Many of the different forges have their own distinctive marks, like a cardinal's head (cardinal), a square (Brass Aluminum Forge), a split "A" (actually an "A" over an "H" for Anchor Harvey), ect.  

The front sight is still the most common form of gas block, and not everyone has the ability or inclination to change their gas block, but are using an optic as their primary sighting system.

In a pinch, you can shoot with the front sight only, or use an INOP optic as a large "ghost ring" aperture and continue to engage targets.  

~Augee

Large ghost ring! Why didn't I thought about that!!

Genius! Maybe a bit inaccurate!

You certainly won't be winning any matches like that, but with practice, you can engage man-sized targets out to 100m relatively easily like that.  Or at least give them a good reason to keep their heads down.  

~Augee

I don't think he's referring to forge marks.  

OP, are you talking about stickers or patches or the like?

The Ace of Spades las long been held to the the death card, a good luck charm, etc, in a military context.  A bunch of units have used it in the patches.

Exactly I'm not thinking aboutthe forge marks, but the patches and stickers. The last one I saw was on a M4 lower, think it was laser engraved into the lower.