Hammer falling to half cock

[Ragnar175]

Alright guys I need some help. I picked up an STI Trubor and it worked fine upon arrival. I swapped the grip for a DVC grip and now I’m getting one in every 10 or less trigger pulls where either the trigger locks up and I can’t make the hammer fall, or the hammer falls to the half cock position. Also, the slide gets stuck occasionally when racking the gun with no mag. A quick little shake or re-rack sends it forward, but it’s clearly not normal. Any advice would be greatly appreciated! 

[Joe4d]

well normally hammer follow is caused by a bad trigger job, or a worn trigger job on the sear hammer interface, or a weak or again overly thinned or polished sear spring. But then, it usually falls to half cock. 
In your case, as it started right after you changed grips, Id backtrack , put the old grip back on, see if problem goes away.
Just from looking at that picture, I am wondering if the grip is hitting the safety and not letting it fully disengage.

[TimBoettcher]

The trigger is stopping the full stroke of the bow... back off the overtravel screw 1/2 turn, that should do it!

 

 

Tim

[CSEMARTIN]

I remember reading in multiple threads on hammer follow that the grip screws on these wide bodies can cause an issue.  There are several hammer follow threads full of good information on things you can look for. The one thing I didn't see mentioned very often was the hammer spring.  Another idea was to place a piece of masking tape on the sear spring to snug up the contact between the sear spring and the MSH.  Check your hammer hook depth with a feller gauge and make sure it is at least 18 thousandths.  The sear should make equal contact with the hooks.  You might try adding more pressure the the sear leg(left) of the sear spring.  Check to make sure the hammer hooks are square.  You may also be getting trigger bounce.  Also, check the mainspring cap.  Sometimes the strut can chew it up and I have read here that-that can cause an issue.

 

There a lots of things that can cause hammer follow, and there are several threads on this topic that are very helpful.

 

Good luck.

[magpulled]

Sear spring  could be to short as well and moving around in the grip. Hammer strut could be an issue too. 

These are a couple issues I’ve ran in to. 

[theWacoKid]

It's your grip. It's the most common cause of your problems. Specifically the location of the sear spring. This occurs when grips sag in the rear, pull away in the rear, or tolerances stack up and allow the sear spring to locate too low. 

[sauza45]

Was the grip new, if not check for cracks and also check to see if the grip screws are tight. Also check your overtravel adjustment.

[Ragnar175]

9 minutes ago, sauza45 said:

Was the grip new, if not check for cracks and also check to see if the grip screws are tight. Also check your overtravel adjustment.

Yep, the grip was new. Screws are tight. I’ll try adjusting the overtravel and see if that helps. Thanks!

[sauza45]

To check and adjust overtravel screw, cock hammer and hold the hammer back, pull the trigger and hold the trigger back, now rock the hammer you should not fell any bump from the sear.

You can turn the screw in until you just feel the bump and then back off 1/2 turn.

[TONY BARONE]

Left leaf of sear spring could be hanging up on the grip.

[Hiroshi]

Check and see if your trigger bow is binding on your new grip, you might be dealing with fit issues on the trigger bow.

[Ragnar175]

Figured it out after an entire day of diagnosing the issue with the help of Bad Dog Custom guns. The disconnector spring was at too shallow of an angle and was binding the disconnector no matter how much tension was set. My slide was also getting caught on the top of the disconnector causing it to randomly lock to the rear. Some light filing of the top of the disconnector and leading edge of the slide (bottom of the breach face) fixed that. Big thanks to Bad Dog Custom Guns for all the help! If anyone needs a very knowledgeable smith, hit him up!