Both a 1919A4 in .22 Long Rifle and a Browning M2 in .22 Mag were originally manufactured by Tippman Arms in the 1980s. The 1986 ban on the new manufacture of machineguns put a serious damper in their business, as a semi beltfed .22 is really nowhere near as much fun as a full auto. They were also fairly expensive back then at something like $1,200.
My friend Eric Graetz of Lakeside Machine bought all the remaining parts and tooling. He manufactured a very few Post samples, (not many Police forces are interested in a beltfed .22, but some did get transferred as "training aids").
Eric now dedicates himself to making beltfed uppers for the AR platform, which allows anybody with a registered lower to have fun with an inexpensive to shoot .22 beltfed gun. Semi is also possible, but I just don't see the fun in that.
Hs website is rudimentary, but here it is for those interested.
http://www.lakesideguns.com/