Pistol caliber lever guns are the original assault rifles. The first of the breed was the Henry repeating rifle of 1860. Its cartridge was the .44 Henry Flat rimfire. While the .44 Henry was not a "pistol" cartridge in the sense that it was originally chambered for a handgun, it was a large caliber, short round with ballistics that would today place it squarely in the handgun category. The Henry rifle held 14 rounds, and its high rate of fire made it greatly feared. It was known to the rebs as "that damn Yankee rifle" and "the rifle you could load on Sunday and shoot all week."
So let's see: lower power cartridge than a rifle, with shorter range, but large capacity and high rate of fire. Yup -- the original assault rifle.
The "Improved Henry" (aka the Yellowboy or the 1866 Winchester) came next, with improvements such as a loading gate on the receiver and a wood forearm. It was followed in 1873 by the rifle that "won the west" -- the Winchester 1873. The 1873 Winchester used a new centerfire cartridge that is now known as the 44-40. Again, while it is technically a rifle cartridge in the sense that it was designed for a rifle, it is a short, fat cartridge that throws a large caliber, heavy bullet at subsonic velocities, i.e., a pistol cartridge. The original 44-40 closely matches the later .44 special cartridge in many respects. While originally offered in rifles, revolver makes (including Colt and Remington) soon offered six shooters chambered in 44-40.
So why were the first lever action rifles designed for pistol cartridges? In part, it was because the original action designs could not handle the high pressures of larger and more powerful cartridges. Once stronger actions came along, however, pistol caliber lever rifles remained popular for the same reasons they were first popular -- they are compact, lightweight, fast handling, and have large magazine capacities.
Rifle cartridges tend to be much longer than pistol cartridges. That's a problem with tubular magazines, because cartridge length determines the magazine capacity. A rifle with a 19-20" barrel that will easily hold 10 or more pistol cartridges in its magazine will hold just five or six rifle cartridges.
The longer cartridges also require longer bolts, longer carriers/lifters, and lengthened receivers to hold that hardware. The receiver, barrel, bolt and locking lugs on rifles intended for use with rifle cartridges also have to be beefier to handle the higher pressures of rifle cartridges. That all adds up. By the time you take the sleek, lightweight, fast handling, high capacity pistol caliber lever rifle and modify it to handle rifle cartridges, you end up with a heavier, slower handling, clunkier, and lower capacity rifle.
Finally, rifle cartridges typically depend on high velocity to deliver energy, whereas pistol cartridges rely less on velocity but make up for it through heavy bullets that travel more slowly. The import of this distinction is that rifle cartridges need bullets that are aerodynamically efficient in order to maintain their energy. The force required to overcome aerodynamic drag increases with the square of the velocity, so it takes four times as much force to move an identical bullet twice as fast. Thus, rifle bullets, which have to move fast to deliver energy to the target, need to have efficient shapes like spitzers. Unfortunately, you can't use pointed bullets in tubular magazines, because the point of the bullet may set off the cartridge in front of it under recoil. Since lever action rifles have typically relied on tubular magazines, that severely limits bullet choice. That's not a handicap for pistol calibers, but it is for rifle calibers. Some manufacturers have built rotary or box magazine lever actions (Winchester 1895 and Savage 99, for example) to allow the use of pointed bullets, but they tend to lose lots of the elegance and handling properties that otherwise make lever actions so great.
More recently, Hornady has introduced the LeveRevolution line of rifle cartridges designed for tubular magazines. They use soft polymer pointed tips so they are safe in tubular mags while improving ballistics. You still have the issue of long cartridges, however, which give up a lot of mag capacity to pistol cartridges, and require heavier actions.
So there you have it. Pistol caliber lever guns exist because they are lightweight, fast handling, reliable, and can deliver a lot of ammo on target quickly and reliably. Yes, they are short range guns due to the inherent ballistic properties of the cartridges, but by "short range" I mean 250 yards and under. In the right hands, .44 Magnum lever guns are very effective on deer sized game to that distance, and perfectly capable of doing the job.
. That was the start of it. :banghead: 
