So, to my knowledge, the power and propulsion of a bullet comes from the explosive in it, which is triggered by firing the gun. So why is it that some guns are considered more powerful than others using the same ammunition? Isn’t the gun just „hammering“ the round to make it explode?
Sorry if I got any terminology wrong, I‘m not a native speaker.
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Length of the barrel, the twist of the rifleing of the barrel, the shape of the chamber and tightness of the upper reciever all contribute to the resulting balistics of any given round.
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The length of the barrel makes a big difference. The longer a bullet is in the barrel the longer the force from the explosion acts on it, meaning a faster exit velocity from the barrel.
The barrel is a part of it, primarily lengths. Ar-15 style rifles come in a wide variety of lengths from 8 inch pistols to 20 inch rifles.
That 12 inches of room has a big impact on velocity with how much time that bullet has pressure behind it.
10.5 to 16 inch is what a lot of people choose for various reasons and various needs. If someone is looking for the max range from that bullet, they might go with a 16 inch. If someone is looking for better handling (less weight up front) they might go with a 10.5.
There’s also tiny differences in stuff such as rifling (the spin the barrel has), different types or thicknesses of the barrel itself, and tiny differences in quality based on different brands..
i wonder how much activity lowers in this sub as chat got gets better.
A longer barrel mean that the propellant gas of the ammo have more time to push the bullet which mean the bullet will have an higher velocity.
There is also some ammo with higher pressure, aka they have more propellant in their cartridge and not all guns are designed to resist that level of pressure. We typically called those ammo overpressure cartridges, the 9mm +P or 9mm +P+ for example. The new US 6.8mm is another example, right now only one gun is using it which can use both the brass and overpressure hybrid version of the ammo, but I wouldn’t be surprised if future civilian version of the gun were only designed for the brass ammo. Lower pressure mean less wear and tear and less need for heavy duty pieces that are more expensive.
There is also a lot of other factors about a gun that might important the power of the bullet, but others aspects like accuracy.
If you just took a pin and hammered at a round, do you think the bullet will fly far or accurately?
You need a barrel to channel the “explosion”, and different guns have different barrels.
Tldr: because physics.
There’s a lot of factors that contribute to how much power a weapon has;
The ammunition itself has a maximum output that can’t be exceeded, but can fall short if other factors fall short.
The barrel length is probably the biggest contributor, when you pull the trigger, the propellant explodes and pushes the projectile down the barrel, the longer the barrel, to more space the expanding gasses have to push the projectile. For example, a pistol has a barrel length of maybe 15cm (6″), so the projectile gets pushed for 15cm then it leaves the barrel and the gasses escape sideways. But a rifle has a barrel of say…60cm (24″), or 4x what the pistol has, so the projectile gets pushed for 4x the distance before the gasses escape sideways, the rifle isn’t 4x more powerful as the majority of the pushing happens at the beginning, in the first 20ish cm (the more powerful the ammunition is, the further this lasts), but it’s still a more powerful weapon, even if it has pistol ammo.
Rifling is a spiral on the inside of the barrel, the longer the barrel, the more time a projectile has to have the spin imparted to it, affecting accuracy.
What these tend to mean on practice however, is that less powerful ammo is used in pistols, partially for recoil and handling purposes, but mainly because the barrel is too short to get the most out of it. But larger weapons have larger, more powerful ammo, as their barrel is long enough to get the most out of the ammo, and the weapon itself is heavy enough to help with recoil and handling.
There’s more factors like recoil system, or barrel attachments that effect it in different ways, but I think I covered the main things.
While what many are saying about barrel length and rifling twist etc do have some impact, for the most part what you are saying sounds like something from a video game and video games are often horribly wrong compared to reality. For example a .30 caliber sniper rifle is going to do essentially the same damage battle rifle cambered in the same round, whereas in a video game there is often a “balancing” of damage for play reasons. A 9×19mm Parabellum with the same specs (powder, grains of bullet weight) is going to do almost the same amount of damage in a semiautomatic pistol and a sub-machine gun. A carbine chambered in 9x19mm with a 16″ barrel you might squeeze out an extra 100 fps.
Yes you might get a few feet per second difference from different barrel lengths but that depends on the type of ammo you are using and the burn rates of the propellant. Faster burn rate means that the length of the barrel matters less.
The amount of energy delivered on target is MOSTLY a factor of the round itself with some few percentages different depending on the barrel and other firearm factors. The main difference between weapons is the ergonomics, build quality, rate of fire, inherent accuracy, weight, build cost, retail cost, and of course reliability.
You would have been better off asking in one of the firearms subs.
Another thing not touched on are barrel harmonics, the barrel flexes and vibrates when the round is ignited and as it travels through the barrel. The different profiles of barrels are optimized for different use cases. Even what the barrel is made out of affects ballistics.
You might have a heavy profile barrel on something that isn’t being carried much like a rifle meant for precision accuracy. You would have a lighter barrel on something you carry on you like a hunting rifle or patrol rifle.
The heavier barrel will have less flex, it will have less POI shift as it heats up, mainly because due to its thicker profile it doesn’t heat up as fast.
The gun gets kinetic energy from the compressed gas behind it pushing on it. The gas is so compressed because of a chemical reaction that both creates and superheats that gas.
A longer barrel (up to a limit) lets the gases push on the bullet for longer.
Sometimes guns trade pure power for other conveniences like full-auto (which uses some of that gas pressure to cycle the gun) or add rifling (where some of the pressure spins the bullet to make it fly straighter.