I am one of those "quasi" experts on body armor. I never worked for a body armor company nor am I a scientists or engineer, but I am a dealer of body armor and have shot plenty of it at the range. I am very well read on the topic.
First, if you want to get real answers about armor than the internet is the worst place. You can go ahead and email the company representatives directly. I know if you email Point Blank they will gladly answer your questions in great detail about any of their products. You get answers right from the people who design these vests and work at making body armor from day to day.
Second, lets talk about body armor basics. There are two basic measures of armor. #1) Whether or not it will stop the round #2) If it does stop the round, than is the pressure to the person wearing it at an acceptable level. Let me give you a quick demonstration of what I mean by "pressure".
http://youtu.be/tdPBP9NFFac
This is a European made vest that is being demonstrated. They have different standards overseas, but in a lot of ways they are very similar. In the video, it looks like the man is probably wearing the equivalent of a Level II vest. Notice when the man gets shot, he is stunned for about 10 seconds. The bullet does not go through, but the resulting pressure hits the man as if someone punched him in the gut hard. A 9mm pistol is being utilized for the demonstration. Now a .44 Magnum may not go through, but its going to hit this man with twice the force probably putting him out of action for a good minute or more and maybe even causing internal bleeding from the resulting force.
So the reason why people wear IIIA armor and/or large trauma plates is not only to protect against a larger round, but to reduce the time that you are stunned so you can deliver a counter attack. An officer wearing IIA armor who gets hit with the 9mm is going to be out of action for 20-30 seconds or more whereas an officer wearing IIIA with the 8X10 special threat plates may not be out of action at all.
Third, body armor is generally uncomfortable and is not "concealable". The body armor carrier designs have improved greatly over the years resulting in a more comfortable armor, but they are all still very uncomfortable. Each vest comes in a waterproof bag and the internals of the vest itself consist of many layers. Wearing a IIIA vest is about equivalent to wearing a nice down jacket in terms of heat. You dont see many officers nowadays wearing a big winter jacket and thats because their vest gives them all the heat they need.
The IIIA vest makes you look like a linebacker and its easy to spot someone wearing one of those from blocks away. The II vest is also obvious to see. The IIA is the most concealable, but the astute person will wonder what you have on under your clothes. The only real way to conceal body armor is during winter time under heavy clothes. During the summer, its next to impossible.
Professional users of body armor all complain about having to wear the armor all day. Some professional users have switched to an external vest because its not so close to the body and air can get through a lot easier behind the vest. If you tried to wear armor all day you would change your mind about wearing a vest. Its not comfortable at all and makes you look 2 sizes larger then you are.
Fourth, the vest only covers so much of your body. There are little spaces like above your neck, your armpits, your groin, legs and arms which can be easily hit...not to mention your head. Plenty of officers have been shot and killed despite wearing the vest.
Finally, to answer your question the vest will stop all of the rounds you mentioned. In carbine form though it may not. Here is a youtube video which demonstrates a variety of rounds which were stopped by the IIA vest. The 44 Magnum and 45 ACP were stopped by the IIA vest, but when the 44 Mag went into a 20 inch lever action carbine it went right through. Keep in mind the force generated by the .44 Magnum in the pistol or the 00 Buck in the video would be enough to crack ribs and cause internal bleeding not to mention you would be buckled up on the ground in great pain.
http://youtu.be/KZN97VHvot0
Many professional users in risky areas opt for IIIA with hard special threat plates because if shot then they can immediately respond. Anything less and they might be in some pain stunned and, in that time, the other person can shoot a few more rounds.
