You can go down a dark and winding road quite easily.
It's all about physics.
Heavier bullets hold their velocity better than light bullets. Shooting long range? Better get a heavy.
Heavier bullets are harder to stop than light bullets. Heavy bullets mean deep penetration for hunters. Middleweights offer moderate penetration for self defense. Zippy lightweights make for poor penetration but work great for paper targets.
You can only get so heavy before things get out of control. I don't think a 22 grain bullet tipping the scales at 190 grains would be very easy to use. However, it's a great weight to use for long range 30 caliber targets. It is a fine weight for self defense too but you want to spread out the surface area so it does more damage to the bad guy instead of zipping right through like an ice pick.
Old ammo designs like the 45-70, 44-40, and 45 Colt have big bullets and fat cases because the metals of the day would not hold heavy pressure without getting huge and bulky. To put down a critter you needed a heavy slug of lead doing significant damage. That meant a big fat frontal area. They had to use a bunch of black powder to do what we manage today with small amounts of smokeless powder.
As the years go by, metals improve, powders develop, and performance goes up.
Each cartridge developed for it's own reason. They're kinda like designer clothes. What appeals to one may not appeal to another.
You got pretty close when you suggested the bullet was a cork. That is EXACTLY what it does. It plugs the only avenue of escape for a bunch of burning powder. In fact, how tightly a bullet is stuffed in a case changes the characteristics of the powder burn. Some powders need help building pressure and putting a heavy crimp on a bullet helps do just that.
The powder provides the power but not like many would think.
Most people (including lots of shooters) don't realize is that modern smokeless powder doesn't go *BOOM* like the cartoons unless the pressure is contained. I demonstrated this to friends many years ago but pouring a bit of smokeless powder in a piece of paper and folding it up. When lit, it burned like, well, a piece of paper. The smoke was smellier and the flames had a bit of a different color but there was no crazy burn. If that same charge had been restrained by the chamber in a gun and the bullet acting like a cork things would have been WAY different.
Fireworks operate on the same principle. If you were to cut open one of your Black Cat poppers and dump the powder out it would not pop when lit. It would burn like fizzly paper. That paper casing holds back the burn. Pressure builds and it goes boom. Now, this happens VERY rapidly but that's how it works.
If you need a bullet to go fast the pressure has to be big. There is a limit on how much pressure a gun can hold. If you've topped it out and still want more the answer is a bigger cartridge case. You still have the same limit but you can use a powder that burns slower. It will make the same peak pressure but it takes longer to do it. This means it pushes hard for a longer period of time. More gas is shoving the bullet down the tube.
Dig back into your physics class and pull out that phrase
area under the curve. Yes, an old bell curve. That's what the cartridge designers are dealing with.
You also get into getting as much a possible from as little gun as possible and things really get twisted around.
I think that's a wee bit more than you asked but maybe it'll help understand what is going on.
Clear as mud?
