I’m betting a large portion of the firearms industry would wish Magpul would just stop it. Magpul started as a company that made these handy little things that made reloading easier, and then they kept expanding.
One of the domains they’ve stepped into is slings. Magpul produces the MS series of slings, and MS stands for Magpul Sling. I’ve been using the MS1 for quite some time, dropping it on and off several firearms.

I took it to War Hogg Tactical’s Rifle/Pistol CQB course for two days of live fire and sim training inside a shoot house. I used it for the entire two days and have a good feel for the sling’s strengths and weaknesses.
The Magpul MS1: Lay It Out
The Magpul MS1 is largely a modern tactical two-point sling. It attaches to two points on the rifle and straps across your body. The MS1 is not just a two-point, though; it has a neat trick: it converts into a one-point.
The front of the sling has a paraclip that can be removed from your sling swivel and attached to a ring-shaped bracket at the rear of your sling. This converts it into a one-point sling. If I had to pick one sling, it would be a tactical two-point.

However, the one point can be handy if you are moving in and out of vehicles thanks to the increased maneuverability. Any other time, the tactical two-point is superior. It provides better support and better retention, and when properly tightened, can be a shooting aid for accuracy.
The Magpul MS1 features a slider that allows you to rapidly adjust the sling from loose to tight. Depending on how you adjust the sling, you can get different results. I run my sling so that when it is in its loosest position, it is still tight enough to press the gun against my body, creating tension and stability.

When I run it tight, it is completely hands-free. I can release the gun to overcome any obstacles. That obstacle might be climbing over a low wall or eating a sandwich. It all depends on the day. Since I can convert to a one-point position for maximum mobility, I prefer to keep the sling tight.
The MS1 At The Range
The MS1 provided me with the support I needed to shoot for 8 hours. A modern 5.56 rifle is not heavy or recoil-heavy, but it gets heavy after a full day of shooting in the sun and rain.
The sling helped me perform. The MS1 helped keep the rifle up, shooting hundreds and hundreds of rounds and making sure those rounds went where I wanted them. That extra tension and support helped remove that human error, and eliminating human error should be the goal of any accessory.

The MS1’s ability to tighten and loosen with ease makes it easy to shoot and move, especially when you are pivoting and shooting inside a room. We did not practice switching shoulders, but this sling allows that easily when set up properly.

The slider glides smoothly; nothing gets stuck as you pull or push it. What I did not like was how small the slider is. Many slings use pull tabs that are easier to reach and pull to tighten the sling. A few times, I lost the slider behind my back and had to feel to find it. It is not a big deal, and the slider will not get caught on gear as a tab will. It is one of those personal choices you will have to make.
More than Shooting
The MS1 works well when you are doing the cool shooting stuff, but what about all the other stuff you do with a rifle? The walking, the carrying, the standing around?

It scores high in that category. The sling is 1.25 inches thick, giving it enough girth to keep a basic rifle from digging into your shoulders and back. It might need a pad for an M240, but I am not carrying one of those anymore.
The material is somewhat soft, so it does not chafe. After day one, I was sunburned, and it did not seem to irritate the sunburn that I can recall. It is comfy, and it is perfect for those hurry up and wait, and wait, and wait times.
Going Magpul
One thing about Magpul is that they never release crap gear. You can assume from the start that anything with the Magpul branding is a quality product, and the MS1 is no different.

The Magpul MS1 provides a fantastic, modern, easily adjustable sling. Sure, the slider can be tough to find at times, but beyond that, the MS1 is modular, well-made, and comfy.