In Gears of War 3 for the Xbox 360, you can unlock the Big Explosions mutator, which will make the radius of explosions much larger than normal, but cut your experience gained by 25%.
To unlock the Big Explosions mutator, you need to earn 100 Hail Mary ribbons. Hail Mary ribbons are earned in versus matches by getting kills with the Boomshot from 200 feet away. I have written a guide that explains an easy way to get Hail Mary ribbons if you’re having trouble.
Check out my other guide if you’re looking for the full list of unlockable mutators in Gears of War 3.