I'm not sure that the OP really understands how unpleasant armor actually is. I carry a pistol that's about as heavy as they get. Right around 48 oz loaded weight. I generally carry at least one reload for it. there's another ten ounces. Now, if I downgrade in caliber alone, I can shave a few ounces. That still doesn't give me a vest's worth of weight. If I shift from steel to polymer or aluminum, I can probably shave another ten ounces. Show me the twenty ounce vest? I haven't seen one, yet. So I still haven't shaved enough weight to make up for downgrading both the useability and effectiveness of my weapon. But I'm still carrying a fullsize weapon, albeit lighter in weight and caliber. maybe if I start shrinking the gun, as well, I can shave down to where I've saved enough weight to make up for the vest. Ok, chop off half the slide, and half the grip. Now, I can barely get a grip on the gun, the sight radius is so short that it's a challenge to shoot the thing well at the range, let alone in a stressful situation, and it's still not very effective in caliber. But, how much weight have I saved? Let's see, we've gone from a 48 oz fullsize 1911, down to a supercompact small caliber weapon. Let's call it a Kel-Tec P32, just because I happen to have one for comparison. It weighs in at about 10 oz. So, I've just shaved 38 oz, or not quite two and a half pounds. I've decreased the effectiveness of my sidearm from fairly decent, for a handgun, to "better than trhowing rocks." It still hasn't given me the weight savings for a vest, as they generally start at about 3 pounds.
This doesn't even begin to address the comfort issues. A big heavy gun isn't really a bad deal, if you've got decent leather to carry it in. In summer, I can hide it under a big t-shirt, if i want to. Not really a lot of change, as far as heat or unpleasantness. Do I really want to trade that in for binding, chafing, smelling and hot as heck armor? Nope. I think I'll stick with my present defense plan. Cell phone, running shoes, and an big, easy to shoot pistol.
~~~Mat