I am unaware of LE use of MagSafe, but I've shot a lot of it and carried it some, but not for many years. Joe Zambone and his family originally made MagSafe ammo, in lots of different configurations for lots of different calibers. Most of it was various sizes of lead shot embedded in epoxy, inside a conventional bullet jacket. Some was an epoxy-only core. All of it was loaded hot, some REALLY hot. I was always a little dubious of its penetration potential, but it fragmented spectacularly in water, gelatin and meat. The bullets are so light that they tend to hit very low, especially in revolvers, which is one reason I quit carrying it. The other reason was my concerns regarding underpenetration.
Joe sold the company to some folks down in Florida some years back, and they cut back on the variety of loads and calibers. I have little experience with the ammo made by the newer company, but Joe trained them personally, so they should know how to make it. Tragically, Joe bled to death after breaking a leg in a motorcycle accident in Australia several years ago.