i have the Ultimate Force chest Protector (see like below). how is this different a bounce vest? or is it a cheap bounce vest and i didn't know it
The words Bounce Vest and Chest Protectors in my view are used interchangeably. A true Chest protector is designed to protect you from the impact of paintballs, but these tend to be made from hard materials like the NXE Chest Protectors which is made from hard plastic. You will feel the paintball impact, but you won't get any bruises. The downside is that the paintball is almost certain to burst on impact.
Bounce Vests are there to promote the "bounce" of the paintball, so you get hit, and the paintball bounces, and does not burst keeping you in the game. The Dye Chest Protector is a good example of a true "Bounce Vest" (IMO). So you will definitely feel the paintball impact, and you will likely still carry a bruise (but much reduced), but you are still in the game.
The Ultimate Force Chest Protector and the Empire THT Grind and Battle tested chest protectors are again in my opinion "hybrids" they have foam padding designed to spread the impact of a paintball (reduce the chance of a bruise), and promote the "bounce" of the paintball keeping you in the game. The foam is not as soft as that in the Dye so the chances of the paintball "bursting" on you is greater, but you benefit from slightly greater protection.
Hustle Paintball did a good Chest Protector video on You Tube, where they shot one of there team at close range with paintballs, while wearing different Chest Protectors, and bounce vests. It is a couple of years old but still fun to watch. The person who was shot at close range even let them film his chest with the bruises he received from each bounce vest with a pain rating, to allow you to make a better buying decision.