I saw a video the other day where a fellow was complaining that chain brakes are useless. He was demonstrating how he formed his opinion by doing kickbacks with his saw with his bar vertical. That launches a kickback right at your face, and luckily, he never made a serious kickback, because a bad one is powerful. His brake probably was fine, and he wasn't hitting wood hard enough to make it set. Sometimes when doing a demonstration you may have to hit several times to get the effect you want, but if you do, you must have your saw turned so it launches to your right, not vertically at your head. A strong hit will swing the saw several feet. Here's instructor Joe Glenn demonstrating a kickback at one of the classes he taught.
The next video shows me out in the woods to cut up a black oak, and I show how to check your brake to make sure it operates correctly.

