Mission Adapted Design Inc. is a fairly new company which is based out of Portland, OR. They have recently introduced a rear sling attachment that is known as the MAD Hook Up. The mount consists of two parts which clamp together over the lower receiver extension (commonly referred to as a buffer tube). The bottom loop will accommodate several different types of sling attachments, to include: HK style hooks, MASH hooks, Snap hooks and standard sling webbing. This will work with most single and two point slings. Cost is $40, with free shipping.
The package includes the two-piece mount, two cap screws that are pre-treated with Vibra-TITE thread locker, an Allen wrench and an alcohol prep-pad to clean off the attachment point prior to installation.
CNC machines form the two clamp pieces out of a block of steel and the parts are then sent to Burlington Engineering for their Melonite finish. This was interesting to me, since the process yields a finish that is highly corrosion and wear resistant. The parts run about .450" thick and the loop is just a hair over 2" at the widest point. The manufacturer lists the weight at 1.74 ounces.
The mount does not require the removal of the receiver extension, which is perfect for those folks who don't want to remove the staked on receiver extension nut or end plate. For LE or Mil issued carbines, regulations typically prohibit the removal of the such parts and the MAD requires no permanent modification to the weapon, so it's more likely to get the stamp of approval by the armorer or chain of command.
Installation took all of about two minutes on a Colt carbine, with a mil-spec receiver extension. The manufacturer indicates it will also work with a commercial receiver extension. The mount was used in conjunction with a Gear Sector GS 2P sling with the HK Snap Hook adapter.
The wide loop on the bottom of the mount allows the sling hook to slide to either side without catching on anything, making transitions to the opposite side easier. I was initially concerned that the bottom loop would protrude excessively and possibly interfere with manipulations, but I did not find that to be the case. However, my left middle finger did occasionally contact the left side of the upper half of the mount, when operating the changing handle. This did not induce any malfunctions.
The mount does prevent the stock from locking into the closed position, but I typically run my stock one click out from closed. This was one of those parts that I wasn't really sold on at first, but then after spending some time with it, I've decided it will be staying in place on the Colt. With that said, I did wonder if the part could be slightly downsized, without compromising function.
Here's a comparison picture of the Magpul ASaP ambi sling attachment point with the MAD hook up sling mount. I just got one to T&E and will be running for the next few month. As Eric pointed out previously, the MAD sling was quick to install and is well made. The MAD hook up sling mount is on the top and the Magpul ASaP sling mount is the bottom.