Archangel14, I was first to admit my first post to the topic was harsh. But rather than hide behind the edit button I let my comments stand and admitted to being a bit over stated when I re-read it later. I see so many folks type things here then edit their statements significantly after the fact, I choose to not do that, but also be the first to call B.S. on myself if it is warranted.
I will delve a bit into the subject due to extensive knowledge to see if this helps you discuss the subject with your friend. I am also going to follow my listing of threat level definitions with some personal observations in the event someone has interest. Stop reading when you get bored. A simple read of the NIJ standards will clear up most questions but not all. With proper caliber, bullet type does not significantly matter within a vests rating but velocity is super critical. Threat 3 will stop most any handgun even big magnums with hard cast and Threat 4 will stop multiple hits of 30-06 AP. Threat Level 3A and under are where vests become handgun caliber specific. So the question really lies in what vest a person may be wearing. Threat II can be compromised by +P 9mm. Someone wheels out a 454 casull mag bullet choice isn't going to matter to most vests 3a and under. It will shred it. So personally my opinion is you cant turn a .38 snubby. .45 acp or most pistols into a vest killer with hard cast bullets. In
most circumstances the caliber in question will either do it with most common bullets or with none. That said, you can turn most center-fire handguns into something they were not intended to do with ingenuity beyond simple hard cast bullets.
There are trauma plates that are rated to stop multiple hits of 30-06 AP and above. Some vests are so good that the military has banned them as most Colonels and Generals with the cash were choosing to purchase said vests which was deemed unfair to the rank and file troops who could not afford non issue equipment. Was not just the brass either as some more affluent families were sending their kids some of these vests out of pocket. I got caught up in this when I sent my nephew a package that contained a set of multi hit AP trauma plates, a Randal Model 15 Airman Combat Knife and a few other goodies. He had to send the plates back but got to keep the rest. I know that certain special ops teams are using beyond Level 4 vests that are beyond what is declassified materials. But that will always be the case for those special guys that put themselves in the worst possible scenarios voluntarily.
Now to the nitty gritty part of vests. Every level you step up, except in certain very expensive options, you give up mobility and add weight. Some vests that will stop a .357 magnum will not stop a knife. Some Level 1 vests will stop a knife or any edged weapon. These are popular with prison guards that are much more likely to be stabbed than shot. Unless you have more than 2,000 dollars per unit to spend on a vest, most beyond level 3a are heavy and restrictive. Then you have to decide whether to add options such as groin protection, neck protection, nape protection, tail bone, etc. you can get chaps, forearm protection, etc. By that time you look like a cross between the Michelin Man and a bomb disposal guy. Thus the original question of whetehr or not a hard cast bullet will defeat body armor is such a broad question it is almost impossible to anwer without knowing a persons idea of what level body armor. If your question is that of average street cop Level 2, SWAT Level 3a with plates, Federal Entry Teams Level 4 for a generic answer. Take that and apply to your bullet and caliber of choosing.
Basic specs:
Level 1: 22 lr to .380 acp
Level 2a: 9mm 124 gr 1,000 fps to 40 S&W 180 gr 1,000 fps
Level 2: 9mm 124 gr 1,170 fps to .357 158 gr 1,400 fps
Level 3a: 9mm 124 gr 1,400 fps to .44 mag 240 gr 1,400 fps
Level 3: Up to 7.62 150 gr 2,750 fps
Level 4: Up to 30-06 AP 166 gr 2,850 fps Single shot
I have two vests each for me and the wife. We each have a threat level 2 that as thin as we are will pretty much conceal under a T-shirt/light jacket and is relatively comfortable. I often wear mine as extra protection when riding my motorcycle under my leather coat. Actually had it on when I had a deer run out in front of me on my motorcycle early last spring which put me down and hurt. Without I, the cops and the surgeons are all sure I would have suffered much more damage than I sustained. Of course the carbon fiber helmet, goggles, armored chaps, armored gloves and armored boots helped a lot too. My only damage was a compound fracture of tibia and fibula right at the top of my boot line. Cops and doctors said in most accidents like mine they end up fixing broken ribs, shoulders, hips, etc; not to mention picking gravel, dirt, broken glass and other debris out of multiple wounds. Other than the leg I had not a scratch so a vest is good for more than just bullets.
So we will wear our level 2 vests under our ride rags, especially in cooler and inclimate weather. Also when I have a Telecom job to do in specific areas I sometimes wear mine and if the wife is along she will wear hers too. Unfortunately they have to put cell towers and phone switching equipment in the middle of urban gang areas too. Thus, I consider when going into known gang territory with a new service truck and 100,000 dollars in tools it is not a bad idea. We also both have a Level 3a vest which we seldom wear due to them being bulky. Mostly only when going to a public indoor shooting range. If I happen to go with friends to one specific public range that allows pistols and rifles, I slip my trauma plates into my 3a vest which take my center mass front and rear to full level 3 plus. My wife has never had need to put her trauma plates in as she never goes to this particular range. As you add each level and plate, weight increases, mobility and comfort decreases. If I thought I had the need, I would buy the wife and I each a Pinnacle "dragon skin" vest.
I work around and in Ft. Benning, Bragg, Knox, and others on their Telecom equipment. Usually when around those bases I hit the closest pawn shops to base. A lot of guys pawn their battle wear and declare it missing in action. Basically there is a simple form that troops fill out whenever they rotate back from the Sandpit that can declare anything missing other than rifle with virtually no questions asked and most goes to the pawn shop. I can pick up current issue Kevlar helmets as cheap as 50 bucks sometimes. Current issue combat vests will go for less than a 100 bucks. Gas masks about 50 bucks. My friends love them and I can keep my wife and I current with whatever issue is then trade older generations off. All of this sits in boxes in the gun room in the event something all these survivalists worry about happens. So if any of you are inclined to purchase any protective wear, find the closest base that rotates troops into combat and check the pawn shops. If anyone has any questions about armor I will be more than willing to share more. Like how to get good vests really cheap. I usually pay around 100 bucks for new vests. I will share how to do it.
Loads of good information:
http://www.ceradyne.com/products/defense/advanced-body-armor-systems.aspx
http://www.pinnaclearmor.com/body-armor/dragon-skin/