Re: Must see!!! So awesome!!
There's also the Anzio 20mm rifles, for those who are actually interested in buying one despite the registration of a Destructive Device.
20mm practice rounds are available at roughly 10 bucks a piece while tracers cost about $15.
Rounds with an active warhead, if you even find the stuff available, are DD's all on their own and I think most of the reason you won't find them is because there is hardly any market for rounds that each require a $200 tax stamp. (At that point you might as well buy anti-tank missiles)
Other 20mm rifles are the Finnish Lahti L-39, the Swiss Solothurn S-18 (multiple variants), the Croatian RT-20, the Japanese Type 97 and the Indian Vidhwansak, the latter also capable of firing the Russian 14.5x114mm round also fired by rifles with a similar purpose, such as the Russian PTRS-41 and PTRD-41 and the Aizerbaijani Istiglal.
The difference between the two is that the 14.5 is still officially a machine gun round while 20mm and bigger are cannon rounds and as such have other warheads available.