Why do they noit use the MP5 in Atlantis? After seeing that they need to put an entire magazine of those little 5.56 mm rounds in a wraith to kill him. The 92 FS Beretta with its 9 mm rounds seems to stop a wraith fairly quickly (See episodes Aurora and the Siege Part I.) The MP5 and the UMP and other SMGs that fire the larger rounds are absent form Atlantis, but are still in use on Earth's SG teams occasionally.
Why don't they use anything bigger than a tiny 5.56 mm P90?