Which ammo is being fired?

Blanks ;)

At least one, but probably two characters are firing AK weapons and would be either 7.63x39 or 5.45x39 supposedly. The most visible AK has a bipod in the folded-up position on the gun. One other character seems to have an SMG or carbine with more of a straight stick mag, and might be something like an HK UMP in .45acp, but is impossible to tell.

unleaded gasoline with 2-stroke engine oil; probably 50:1 ratio.

Shots? Lucky guy :-)