In short, a typical subsonic or marginally supersonic sci-fi moving-blob plasma blast would require a magical self-contained containment field, and it would float up into the air even if it did hold together.
Well, since we have alien tech, we could get around having that problem. Or We could just have it firing the plasma itself. I like the idea of having a small layer of metal around an elerium slug, that way, there's two layers of damage - one from the plasma, and the other from te impact of the slug.
DefRev has obtained the original "white paper" proposal that was submitted to the U.S. Army for the Stavatti TIS-1 (Tactical Infantry System-1) Gasdynamic Laser Weapon. The TIS-1 is a laser rifle that utilizes a hypersonic jet of gas to create photonic energy in the form a very powerful laser. Thus the term "gasdynamic". The Stavatti TIS-1 was submitted as a possible technology for the U.S. Army's LFLAN requirement. "LFLAN" stands for "Light Fighter Lethality After Next". LFLAN involves small arms technology proposals that would not be implemented until 15-25 years down the road. In other words, truly futuristic technology.
Before a weapon like the TIS-1 could be adopted, a number of technichal hurdles would have to be successfully negotiated, such as...
a viable power source that could provide long-term and adequate power, heat containment/shielding, and forward recoil mitigation.
This could work as another form of laser weapon, and could replace our current ones.... Google works well for finding suitable ideas for weapons. Here's the Link