Old school here!!! Never used a single point sling!!! What are the advantages, and disadvantages??? The MP15-22 comes stock with one sling attachment which suggests that is what they think most want.
Need some education please!
Guy22

I am a big fan of single point slings and run the blackhawk single point on all my AR's!

The advantage for me is when training and working on transition drills, its easy enough for me to flip the safety, drop my rifle in front of me and grab my pistol. Then simple enough to transition back to rifle.

I think single points, along with three point slings, either you love them or you hate them.

For me for training purposes and transition I like the single points!

HTH

Good luck

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Paracordwraps

The positive of a single point is that it's easy to transition right handed to left handed use. It doesn't get tangled up in your gear or armor. It's cheap and it's easy to use.
Some of the negatives would be that it will frequently break your balls. I mean this in the literal sense because if you let it swing down it has a habit of catching you dead center. It doesn't offer any stablity to your shooting stance like a 2 point would when you tuck your elbow inside of it.
I wouldn't attach a single point to that buckle on the stock. I would want it closer to the receiver somewhere in front of the stock.