Have you ever operationally used a single point sling? They're horrible if you need to move. You have to hold onto the rifle or it flops everywhere.

A two point sling can be tightened so it's not flopping around when you have to move and most have a quick adjust for body armor and heavy jackets.

The front needs a sling mount on the rail. I've used both swivels and fixed. I favor fixed.

Standard M4:


M&P 15 quick fix:



The rear is just threaded thru the stock.



-- Chuck