If these rifles had been around for at least 50 years earlier, why wouldn't the US army, or any army for that matter taken advantage of this technology? In comparison to a bolt action, you do still have to manually reload each shell into the rifle, so i suppose they wouldn't have a huge advantage, but you would think they would have seen a larger use. I can also see how from a cost standpoint they would be more expensive, and they aren't chambered in as large of shells as well. That may have answered my own question, but any input would be interesting. Thanks.
Lever action rifles were poorly suited to advances in bullet manufacture. Most lever action rifles had tubular magazines, were the tip of one cartridge rests against the primer of the next. This was all well and good for round nosed bullets, but towards the end of the 19th century, pointed spitzer bullets came into wide use. In a tubular magazine, there was a risk that recoil could press the primer sharply against the tip of the spitzer bullet, thus detonating a round in the magazine.
The other primary thing is that it is harder to work the action on a lever action rifle while prone(the action being on the bottom of the weapon) than it is to work a bolt action rifle (the action being on top of the weapon) considering how focused on trenches and fortifications being able to fire a weapon prone or from a non-standing position was at a premium.