(don't laugh) An Englishman asks: What makes one gun more powerful than another?
 

My question is: In the simplest terms possible, what is it about one gun that can make it fire a bullet further and faster than another gun firing the same ammo?


That's not the sort of answer I'm looking for.

There are only three general factors that enable one gun to fire the same ammo faster and farther.

1. Rifling. The projectile travels through the barrel and meets spiral grooves designed to impart a longitudinal spin around the axis of travel. This makes the projectile spin like a perfectly thrown football "spiral". Although rifling improves accuracy, the frictional losses actually reduce the total energy of the projectile.

2. Efficiency. The energy of the expanding gasses must be translated into kinetic energy. The better designed weapon will do a better job by transferring the energy of the explosion into energy of the projectile while reducing escaping gasses.

3. Other frictional losses. While all this is going on, the projectile is moving down a barrel. Minimizing barrel/projectile contact will reduce friction, either through a shorter barrel or by shielding the projectile with a thin wall of escaping gas, but at a loss of momentum or accuracy.

Cheers, Peetster, that's exactly what I was asking.

With this knowledge I'm now an 'expert' amongst my peers.

Are you asking why different guns of the same calibre may be more powerful, or why different calibres are more powerful?

(Please note usage of UK spelling of "calibre". I'm biligual - English and American!)

If I recall correctly, a longer barrel actually ends up sending the bullet further down range because while there is more friction (more barrel for the bullet to travel down), the expanding gases have more time to impart energy to the bullet.

It is a balancing act on barrel length. You get to a point of diminishing reutrns as powder ceases and barrel drag becomes more of a factor. It is generally better to make sure that your powder's burn-speed matches your barrel length properly.

Kinetic energy, basically, either faster bullet velocities greating greater energy on impact, or greater bullet weight creating more kinetic energy on impact. Different types of ammo also make a difference as hollow point will mushroom on impact greating a greater size impact, or a different bullet having different penetrating characteristics from the materials used or shape of the bullet.