The M1911-series .45 pistol is semi-automatic only by design.  The pistol incorporates a positive disconnector that is inside the sear that holds the hammer cocked.  The disconnector is designed to prevent: (1) the pistol from firing when the barrel and slide are not locked together (the gun blows-up!) and (2) intentional full-automatic fire.

 

However, I have seen M1911-series pistols go full-auto and it is very dramatic because cyclic rate* is about 1,100 rounds per minute of uncontrolled fire.  The pistols that do this have usually have either a: (1) worn disconnector or (2) someone who doesn't know what they're doing has tried to lighten the pistol's trigger pull.  The .45 I remember that went full auto was a Colt Series 70 .45 Government Model National Match pistol.  In this case, the magazine was stuffed with five rounds and the uncontrolled fire began after the second shot.  However, by the time the pistol ran dry, the muzzle was over the backstop!  The shooter was very embarassed and the gun went to a gunsmith -- pronto.

 

There are several checks that the M1911-series owner must do every time he/she does maintainance on the pistol.  (This also applies to clones of the M1911, such as Kimber, S&W, Wilson, and others.)

 

 

1.  Cock the hammer and set the thumb safety to ON.  Try to pull the trigger.  The hammer stays cocked.  Set the thumb safety to OFF.  Pull the trigger and the hammer falls.  PASS.

 

2.  Pull the slide to the rear and release it to go closed under the power of the recoil spring.  The hammer must stay at full cock.  PASS.  If the hammer follows the slide home and drops to half cock, the pistol is UNSAFE.  Take it to a gunsmith.  You have either a worn sear, worn hammer, and/or worn disconnector.  FAIL.

 

3.  Pull the slide to the rear and release it to go closed under the power of the recoil spring.  Make sure you are not pushing the grip safety in with your hand and try to pull the trigger; the hammer stays cocked.  PASS.  Grip the pistol and push in the grip safety; the hammer falls when the trigger is pulled.  PASS.  If the hammer drops when the grip safety is NOT pushed-in, take the pistol to a gunsmith.  FAIL.

 

4.  Make sure the pistol is unloaded and the magazine is out for this test.  Thumb cock the pistol and pull the trigger; the hammer falls.  PASS.  Thumb cock the hammer again and put the non-shooting hand over the muzzle and push back on the slide to unlock the barrel/slide.  Now, pull the trigger.  The hammer MUST stay cocked.  PASS.  If it goes to half-cock (falls half way down), the pistol is UNSAFE. Take it to a gunsmith.  You have either a worn sear, worn hammer, and/or worn disconnector.  FAIL.

 

There is only one M1911-series pistol clone intended for selective-fire.  That pistol was the Spanish-built Star Model M in 9mm Para.  The pistol had a slide-mounted selector switch and could fire both semi-auto and full-auto.  It was designed to accept a detachable wooden shoulder stock so that the shooter had marginal control in full-auto.  Marginal is the key word here because the shooter could never get more than two pulls of the trigger before the standard magazine (8-rounds) ran out of ammo due to the excessive cyclic rate.  The Star Model M was not built in large numbers and only saw duty with selected Spanish military units.  It was not considered a resounding success by the Spaniards because full-auto fire led to shortened part life and greatly increased the wear on pistols with the feature.

 

(*Note: Cyclic rate is the theoretical maximum rate of fire that full-autos can shoot in one minute if they had a magazine or belt that contained enough ammo.  Cyclic rate is calculated by the length of time it takes to fire a full magazine or a belt of 10 or 20 rounds.  From there it is easy to calculate the cyclic rate in terms of rounds per minute.)