Here's some advice for action scenes: try writing in short, sharp sentences. Keep the actions of each sentence to a minimum, sometimes even just to one single action. This gives the reader the impression that the scene is fast-paced, which most action scenes are (if you want to write, say, a slow-mo fight or a space battle, it's a bit different and a little harder). For example, "The French army approached. Marius struggled to reach for his rifle. Between his fingers, he felt the barrel, then gripped and yanked. He climbed atop the barricade, stuck the rifle against his shoulder, and fired. [i]BANG![/i] The bullet hit a cannoneer. He fell to the cobbles, dead. Marius briefly ducked for cover to reload, then [i]BANG![/i] A musketeer fell. Marius hid and shot, again and again". Of course, once all the action is done with, you can revert back to longer sentences to show that the action's over, though you should probably ease it in e.g. "At last, his rifle was emptied, but it did not matter. The French soldiers were dead". And then, once everything's completely back to normal (character's back on his feet and walking at a normal pace; if he's still in imminent danger or in a hurry, maintain the same, short sentencing), you can go back to long, descriptive sentences, which I can tell you're already good at. Hopes this helps you, and anybody else who might happen to read this.