What is the difference between a M1911 and a M1911A1?

Answer 1

Its formal designation as of 1940 was Automatic Pistol, Caliber .45, M1911 for the original Model of 1911 or Automatic Pistol, Caliber .45, M1911A1 for the M1911A1, adopted in 1924. The designation changed to Pistol, Caliber .45, Automatic, M1911A1 in the Vietnam era. Above taken from Wikipedia the free online encyclopedia. The M1911 has a low and narrow front and rear sight; Curved Flat Mainspring Housing; No Finger Recess behind the trigger; Narrow-Depth Triger; High-Wall Ejection Port; Wide Hammer; Smaller Grip-Safety and some other slight differences. The M1911A1 has a taller and thicker front and rear sight; Round Mainspring Housing; Longer Trigger; Lanyard Loop (May be on M1911 also); Finger Recess behind trigger; Spur Hammer; Longer web-spur on Grip Safety; Heat Treated Forward Upper Reciever; Lowered Ejection Port; Plastic or Walnut Grips. The key differences are the smaller sights on a M1911 upper reciever, and the mainspring housing. These are commonly known as Series-70 models, because they don't have any extra firing pin safety levers. Series-80 models (From Colt), have an internal transfer mechanisim that uses the trigger's rearword force to actuate two small levers that depress a stop plunger in the upper reciever's firing-pin port, that allows the firing pin to move freely when the hammer falls. Kimber's use a very similar, but better designed internal release, that uses the grip safety as a motivator for the firing pin stop. Other companies, like Springfield, use manual locks that prevent the mainstring plunger from moving when the hammer is cocked (The hammer spur moves downward to compress the mainspring. Lock the mainspring plunger and the firearm cannot be cocked. This is not a passive safety, but another method of making an already safe weapon even less reliable, to solve a problem that never existed in the first place... )