The wild barrels on L4 are quite dangerous, especially so the closer you get to Kong, and I'd be willing to bet that you've been directly hit numerous times attempting to grab the top hammer. I'm no expert, but as a general rule it is best to dodge them by moving to the left since they don't bounce as sharply to the left as they do to the right. The other thing to do would be to burn through the screen as fast as possible, perhaps even skipping the top hammer because if you simply reduce the number of barrels Kong throws, the lower the chances are of getting wild barrels to with in the first place (obviously).

Given your high score, I'm pretty sure you have made it to L5 before and you may have noticed that the wild barrels are much more tame and easy to manage. The reason I mention this is that on L4 after 33 seconds have expired on the screen the game will switch difficulty, and you will have L5 style wild barrels to with which is a good thing. Now, what a lot of top players will do on L4 to take advantage of this change in difficulty is to go ahead and grab the bottom hammer to gain some extra points, but more importantly it helps to bide some time so usually by the time you make it to the top and more dangerous part of the screen, the game has already made the difficulty switch to L5 and you aren't going to get assassinated by an unavoidable MSB. Of course, learning to grab the bottom hammer here can present it's own problems and can take a little getting used to, but it's a good tactic to consider. Hope that made sense.