The Magamum! benefits from the high damage of the Torgue barrel and the generous magazine of the Bandit weapon body; being a Bandit weapon, it has heavy recoil and large shot groups, but makes up for this with a very large magazine; a high-quality Magamum! with the Extendified prefix can have a capacity exceeding 80 rounds. While the normal fire rate does not make good use of this, any character build with skills which increase pistol fire rate can make very effective use of a Magamum! at short-to-medium range.
The word "Magamum" appears to be a misspelled version of the word "magnum," a Latin word meaning "great," and a word popularised in modern culture as the name of a large-bore handgun cartridge referenced in the film Dirty Harry.