Traditional competition shooters in NRA/CMP High Power Rifle, Mid-Range, Long Range, benchrest, and other disciplines often single load their firearms during a match (per match rules). In the situation where a firearm uses a detachable magazine, single loading is better facilitated with a magazine follower designed for single loading. While there are followers sold to retrofit an existing magazine, there is also a popular device known as the SLED / Sled (single load enhancement device) made by the Original Bob Sled (OBS) company.
I have used an OBS SLED in the AR-15 extensively during my NRA/CMP Service Rifle competitive career.
Since I recently put together a precision rifle with the ATAICS and have been shooting it in local F-Class matches, I decided to acquire an OBS SLED for Accuracy International pattern chassis systems.
I ordered the Original Bob Sled AI .308 from Brownells. The SLED is your standard fare OBS SLED made out of a solid block of black Delrin. The caveat is that the AI .308 SLED required slight modification to fit in my ATAICS.
The problem I found out of the wrapper is that the AI .308 SLED would not fit into the magazine well. It would be extremely tight and not engage the magazine lock. What I found is that the magazine bump (which is what the magazine release locks onto) on the SLED was too long.
When I measured the length of the magazine from the front to back right on the tip of the magazine bump, it was ~3.105″. But when I measured the distance from the front of the magazine to the tip of the magazine bump, it was ~3.125″. The quick solution was to take a file and remove just enough material to reduce the bump (which I believe is aluminum) to about 3.105″. It only takes a couple minutes to file it down and then to file off the burrs so it won’t cut your hand if you grasp it.
Once I did that, it inserted and locked into place in my ATAICS just fine. It also drops free without issue.
Anyway, if you need a SLED for your Accuracy International pattern chassis system (or your AR-15), I recommend getting an Original Bob Sled. If you have issues with the OBS AI .308 fitting in your chassis, simply measure the magazine bump on the SLED (and compare it to a factory AI magazine or another magazine that fits your chassis) and file the bump accordingly.