In order to get IB gear you need at least IB rank 3

Have yet to see a drop and i have played over 20 games

I saw about 5 assorted drops in about 2.5 (about 15 matches) hours of IB yesterday. Considering 12 people in a match, you could expect to receive a drop of some kind once every 6 hours (35 matches) or so. I don't know the entire range of things that might drop, but if you assume the drop table has 10 different items, all equally likely, then on average it would take 10 times as long to get the item you want. I would guess that if you play 12 hours a day for the rest of IB you have a decent chance to get it, but probably less than 50%.

Hello! Drop rates are dependent on an RNG system. It's near impossible to determine a drop rate for the weapon. Best advice is to keep playing for the best chance to acquire the weapon.