For anyone who’s not the best at shooting I’ve come up with an alternative way of getting this pretty easily. You will want to play Griffball on Halo 3. This will take some time to master the nuances of timing but can become a fun way to attain this. I typically ignore the ball and just go for kills. The interesting thing about this game mode is that if the bomb gets armed and you are nearby you will get kills for nothing. Many times I’ve gotten double kills, killjoys, killing sprees and even exterminations just for being in the vicinity of the explosion. Take advantage of enemy afk players for even more kills and this will come in time. While going for sprees you typically will gain a lot of progress for Double kills and only moderate progress on the other medals I mentioned.
Just a note Griffball on Halo 4 will not cause an explosion after arming a bomb. Also just to be clear, think of the bomb explosion medals as a bonus and not the main way of obtaining them.
Here’s a clip showing you what I mean about being near the bomb and getting free medals.