Lemon squeezers have a grip safety on the backstrap that is depressed when you squeeze the trigger to fire the gun. These guns are hammer less.
A Single Action requires the hammer to be manually cocked before squeezing pressing the trigger to fire the weapon. Double Action only requires you to squeeze the trigger through its entire range of motion from at rest until primer strike.
No. Buffalo do not have dextrous fingers like we humans have, nor do they have the physical capacity to raise a gun to its shoulder to squeeze the trigger. Guns are designed for only humans to use, not other animals.
machine guns were basically used the same way as they are now, but far more dangerous. At the squeeze of a trigger they could fire 500 to 1000 rounds per minute
the trigger
Most guns are semi automatic, meaning that for each trigger pull, one shot is released. other are pump action, requiring a pump before each shot, and some are fully or have ramping automatic, which fire multiple per trigger pull.
Action Guns was created in 1979.
pull the trigger
single action pistol means that the hammer has to be cocked back in order to fire. double action means you merely have to pull the trigger back and the gun will fire. some double action guns can be fired single action or double action.
Assuming you mean "machine guns," when most people use the term, they mean a gun that is fully automatic. That means you can hold the trigger down on the gun and it will continuously cycle the action and fire the bullets that go into the chamber.
On some guns you can change out the trigger springs, others you may have to buy a new trigger or trigger assembly.
It means that each time you pull the trigger, a shot is fired. The other models are: spring/pump action, which need to be recocked after each shot, and automatic which will fire as long as the trigger is pulled.