Why does bullet velocity matter?

You didn't do any math. The travel time difference is less than 10ms (76.9ms for the 650 m/s weapon and 83.3 for the 600 m/s weapon). This is significantly less than the average reaction time of a player and is a small fraction of the TTK. The 50RoF difference makes a much bigger difference - in a second the higher RoF gun will get almost another bullet in the air (10 rounds/s for the 600 rpm gun and 10.83 rounds/s for the 650). If both players are landing all their shots, the RoF will have a much, much greater effect on who actually lives and dies.

That is, of course, assuming both hit all their targets. 10ms isn't much when considering TTK directly, but it is potentially enough to miss a few bullets because the target is running. This is where it comes into play.

Yes, exactly the same thing people miss when they say Adrenaline Pump is "only" 10% speed increase.

50m/s velocity difference probably won't turn a good gun into a useless gun (although 100m/s might), but it will absolutely make a difference.

That is indeed a much better question.

HV on the saber 13.....oooo baby, talk about dem headshots

I remember back in the day when bullet drop actually mattered, indeed, when the VS faction advantage actually was an advantage and not just a gimmick. It was extremely satisfying to play as a sniper back then as when you successfully led your target, accounted for drop, and... HEADSHOT! With the introduction of easy mode sniper rifles such as Longshot/RAMS/parallax(apparently the only way SOE could improve on sniper rifles were to make more powerful and easy to use sniper rifles).

Alas, forumside happend and tons of weapons lost their identity as short/mid/long range weapons. Oh well, those where the days.

Actually, neither win. Since you are assuming 100% accuracy, than both kill shots would have been fired before either side dies. Therefore both people are killed and it is a draw. Also the fact that you had to use such extreme values, shows how little of an impact bullet velocity actually has on TTK.

Use a BASR and you will notice a massive difference.
The Parallax has the highest velocity, only about 50-100 higher than the lower teir BASR.
It's even more noticable when equipping a suppressor. A suppressed Parallax has roughly the same drop as an unsuppressed XM-98.

Alright here's an important question:

How much does the suppressor lower velocity?

Suppressor is 30% I think, and Soft Point is anywhere between 5-15% depending on weapon class.

Yup.

I thought it was obvious, so I didn't say "Except for sniper rifles." Clearly velocity matters there.

Anyway, I got some good answers. I'm still pretty sure velocity won't affect why I choose a gun, ever, but I can see how it could make a small difference (like when a distant target is dancing).

The reason I asked this question is because I saw the latest patch notes with all the minor gun tweaks and thought "Really? Did changing velocity really make a difference in some rifle's performance?"

Velocity only helps in hitting a moving target over a greater distance. All this TTK talk is just BS. It will never be the determining factor in a fire fight, accuracy will, and at the range where higher velocities start to shine recoil and CoF make it a pointless concern regardless. By the time you realize you're being shot at, you'be BEEN getting shot at on the other guy's end. Faster bullets aren't going to compensate for that.

Velocity is mostly only good on sniper rifles and in the ~30m-60m engagement range, where distance is great enough that rounds could be side stepped but not so great that even moderate recoil and CoF is still fairly accurate.