The one I'm thinking about is the Yak 3P, which became the main production variant in mid 1945:
It had 3 × 20 mm Berezin B-20 cannon with about 120 rounds each, still a light load but with a lot more punch. According to Wikipedia: "The three-cannon armament with full ammunition load was actually 11 kg (24 lb) lighter than that of a standard Yak-3, and the one-second burst mass of 3.52 kg (7.74 lb) was greater than that of most contemporary fighters."