this is the wife of the owner of this account. he wanted me to reply to this because of my shooting background.
i started shooting when i was 10. i won the Arizona State Championship, silhouette match, in my division when i was 11. i did it with a Ruger .22 Mark II. this means that i was shooting targets ranging between 20 yards and 60 yards, and doing a pretty decent job of it.
i've shot other guns -- my dad had me shooting his Thompson Center for a while. i've shot other guns, larger calibers before. i'm not really comfortable with anything but the Ruger Mark Series.
so when my husband decided he wanted a gun, i told him that if he was going to learn how to shoot a pistol (he'd only ever gotten good at long-barreled guns), we were getting a Ruger .22 Mark Series, because it's what *i* know i could bring down an intruder in our home with.
if i can shoot a heavy steel target at 60 yards and bring it down, i think i can bring down a man at 10 feet. the first time we went shooting our new gun together, we bought the targets that the indoor range had available, which were man-shaped targets. to prove to my husband what i'd always told him, i put the first shot between the eyes at 20 yards.
i'm sorry, but if you can put one shot between the eyes, you can put other shots elsewhere in the head, heart, abdomen, and groin. that should bring anybody down.
you don't need a huge round, especially if it's something you're not comfortable with. hand me a Ruger Mark II or III, and i can put 10 rounds in a man. hand me a .357 and i'm screwed...and dead. but i think 10 rounds should put him down...unless i'm dealing with the Terminator, in which case i don't think your .44 will help me much either.