Yeah, the K98k is in no way that smooth or fast...it's current iteration in the mod is 100% fine.
Also, the Bren doesn't reload that way (I speak from in person experience with firing and reloading Bren guns). If you did it that way, the catch would catch the mag the moment you take pressure off it, locking the mag back in place. The mag has to be removed by putting continual pressure on the release and rolling the magazine forward and out of the mag well, like with an AK47 mag. The official way to do this is to mash the heel of the palm of your hand up against the mag catch, then roll your palm forward, keeping the heel of the palm holding the catch down and forcing the mag forward and out.