problem is
short range in house multiple attackers best effect
shotgun, rest is discussion of loads and gauge

intermediate range is a lot of attackers within 200 yards
lots to discuss but 223 ammo is plenty and a lot of guns take it

long range 200 yard plus, heavier cartridge straight shooting gun
30-06 or 7mm rifle an M1 is ideal or most good 30-06

real long range 600yards plus a sharps buffalo gun or replica you can purchase, 50 caliber lottsa powder

real close range, within touching distance
pistol various caliber most subjective.

At the video store its a game, this is real, every shot can kill a human being. Get used to the heviest recoil you can stand and fire often. My wife grew up hunting and she didnt get her 410 over and under 22 until she could handle a 3 inch 12 guage without snivelling.

This isnt pretend,
If you pull out a weapon be prepared to fire it
do not fire unless you are willing to kill another human intentionally
be damn sure what you are doing.
please dont be a poster boy for gun control

thanx,
bill