Gun went full auto--HELP

[sutureman]

I had just put in a new Sprinfield Armory hammer into my parts gun (old hammer broke) and when I dropped the slide on a full clip it went full auto on the first two rounds. The books say that this happens when the slide moves forward and when it hits the full forward movement the hammer falls. Now the question is what to do about it and what could be wrong. It also appears that this hammer does not go to the same half cock position as it did with the old hammer. All comments/suggestions will be appreciated!

[usajeep1]

Look at the post "going off half cocked", here in the troubleshooting forum. It might answer your questions....jeep...

[BGregory]

Since the old hammer broke, was there any damage to the sear?
Hammers and sears need to be fitted together and are not "drop in parts".
The change in the half-cock position is indicative of this.
Is the sear spring tensioned correctly?
Is the disconnector ok?

All these should be checked by a reliable gunsmith.

Also, a good practice to follow, which I have posted before, is after doing anything to the trigger group, next time at the range, load 1 round. Check the pistol for proper functioning. Do that a couple of times. Then load 2 and check and keep it up until you are up to a full mag.

Never, ever load a full mag on any pistol the first time firing either after purchasing it or having or doing work on it. Your lucky it didn't go full auto.

[brickeyee]

Most likely a sear problem, and there may be damage to the hammer hooks now also.
Unless you know how to fit a hammer and sear it is probably time for a gunsmith.
The normal production tolerances for 1911 frames result in a few final parts needing fitting unless you want a GI type 8 pound trigger (that is how the problem was avoided on large production runs).
A typical lighter ( 5 pound) trigger requires some polishing and often fitting to make up for the machining tolerances in the hole placement in the frame. The same applies to the grip safety.
These parts may drop into some guns and function, but there cannot be a guarantee due to manufacturing tolerances on both the frame and the components.
Sometime even a few thousandths of an inch is enough to cause problems.
Even using pins to allow outside checkingof hammer-sear angles is not perfect. The holes can be misaligned from side to side in the frame and the outside position does not match the inside position (more of an issue with very low trigger pulls).

[wichaka]

There's a post from D. Kamm in the tech section about doing safety checks prior to going to the range...........I always do them, and still only load 2 rounds after working on the firing group.