Ok, the videos that were posted above do not show this style of brake. In the 75B it is actually a mag brake, it's intended to stop or slow the mag down during ejection of the mag. In the Shadows and similar guns, it's there to protect the mainspring. That's why you had troubles, the one in the videos is a much more flexible piece of metal and much lighter as well, with a curled end that goes down into the mainspring plug's body. The brake you have needs the pin removed first, maybe some pressure on the plug, and then it should simply slide or twist out (the end held in with the pin should pop into the body of the gun when the pin is removed. It stops the plug from coming out if you only take the one pin out that holds the plug in place.
If your mag is scraping against the brake now, when it's all put back together, you need a new brake, as you've probably kinked it or something. But in the pics it looks fine. Some of us, for no real reason, swap to stainless steel mag brakes (they aren't necessary at all). They are cheap regardless.
Sorry for sounding like a ####, trying to be quick and concise with my answers when typing on my phone. Now I am at a keyboard and can be much more verbose.
