Originally Posted by robocop10mm
Not true. A .44 Mag lever action yields significantly higher velocity than an 8" revolver. My 9mm AR gains about 200 fps over the same load in a handgun.
Rifles are dependent on the cartridge. Even the .223/5.56mm has move velocity out of a 20" barrel than a 16". Some calibers like the big magnums need at least 26" for anywhere near max velocity.
Every round has a point that it runs out of power and will slow down once it reaches that point. It depends on a number of factors like bullet size, weight, powder type, powder charge etc. For the 22lr 40 hv it is about 17 inches. past that point it will start to slow down. A 28" barrel will slow down the 22lr round and start to act as a suppressor. There is a major difference between the sound of a 22lr in an 18" barrel and a 28" barrel. For center fire magnums the distance is much longer. I posted a ballistics by the inch chart earlier in the thread. It will give you some idea of where handgun cartridges find their optimal barrel length. Unfortunately it did not cover the 500 S&W. I found that information elsewhere.
I used to reload for my wife's 19" barreled 243. I used a slightly faster burning powder because of the short barrel. My hand loads were quieter than factory loads which were optimized for a 24" barrel and were faster than the factory loads in that barrel.