Just because you lost to an m4 using the bar doesn't make the m4 better, just means the problem is you. Go compare the stats, statistically the only benefit the m4 has is a faster reload and 0.02 more spread which is subjective anyway. Basically the same freeze, same firerate but bar has 10 damage. Whilst 1 more damage doesn't seem like a lot, it most definitely is.
Look at the ghost ripper, the smg mode prior to the nerf was widely considered as an extremely effective and sought after gun. Look at the old stats compared to the 40k tec9 and you will see they are almost the same with the main difference being 1 less damage from the tec9. And yet people don't consider the tec9 equal, better or even use it