Chris I served in the Army and shot with both M2 50cal and MG42 (although in 7,62 NATO ammo). We used tracers regularly and the ones in CoD are by far the most realistic I've ever seen in a game. You're posting videos of cannons that are not using tracers or whose ammunition muzzle speed is way too fast.

As that is not enough, there's been an extensive research on the subject, the conclusion is that 1) you're wrong 2) we're right. Have a look at the fantastic video on the Wellington posted on the main page to have an idea of how realistic it all looks.

Now you can either accept this and go back to your closet or put your head in a pan, smack it with a spoon and go NANANANANANANANANANA!!!

...whichever your option, don't forget you're wrong.