The biggest cause of the 1911 platform is amateurs trying to tweak the sear/disconnector/grip safety spring for a lighter trigger pull. It is critical to performance that it be in balance. Especially the sear engagement, a bit too lite and the hammer following the slide syndrome and full auto firing are the result. The next is the sear-hammer engagement surfaces, they need to be as parallel as possible, smooth faces with sharp edges.
The 1911 was designed to be rugged and reliable, when folks get to tinkering without the proper tools, equipment and skill bad things happen.
The other problem is feeding of ammo other than ball in older guns, the barrel ramp must have the proper geometry for reliable feeding of semi-wadcutter and HP ammo.
The older guns have steeper ramp than the more modern iterations and tends to jam non ball ammo against the top of the chamber. This modification MUST be approached with great caution if foe no other reason than too much material removal leads to dangerous unsupported case heads. A KB from the chamber and break grips and magazines along with hand injuries.
Now don't take my word for it as I have only worked on and/or accurized a few hundred of them and built several "race" guns in my life!
