Here, this’ll probably make your day: MARAUDER plasma railgun. The first simulations were done in 1990, the first real-world test was done in 1993. They estimated that by 2000, their prototype would be capable of firing a plasma toroid at 3% of the speed of light.

My understanding is that the little we know about it is a result of someone either not taking the project seriously, or forgetting to classify the research. The result was that the early research got leaked to the public while the later research is believed to have become classified or top secret, which is why the otherwise successful project suddenly disappeared.