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I decided to enhance my fairly new MkIII with Volquartsen’s : Target trigger, Target sear, Exact edge extractor, and because I have small hands their Extended mag. release and Extended bolt release. I also bought a hammer bushing made by an individual in Canada to replace the Magazine disconnector (note lots of folks on RFC have used this bushing with success).
Now the problem: because I’m terminally inept with mechanical assembly I had a gunsmith install all the parts.
The gun fired beautifully – for 6 rounds then failed to fire at all. Rounds are chambered Ok but the gun fails to fire, the unfired rounds are ejected OK but the bolt became progressively harder to pull back until now it cannot be pulled back at all (I haven’t tried excessive force) and the safety is locked, unmovable, in the “F” position.
Of course it’s going back to the gunsmith but I was wondering if some of the experienced folks here might have some ideas on what may be happening.

It kind of sounds like a hammer pin or sear pin has backed out. Remove the grips and look at the right side, toward the top where the hammer and sear pins are. The hammer pin is held in place by the left grip, if this backs out problems accour.

If the trigger pretravel is not adj correctly it will keep the disconnector from resetting. If it does not reset you can not fire. With the VQ trigger the adj is easy enough to adj. Then again if you do not have enough post travel the trigger will not trip the sear. If loctite was not used the screws can move out of adj.

Welcome to Guntalk!

I have to fully agree with the above post. First, check the hammer pivot pin to ensure that one side has not backed out of the frame, that should resolve your bolt operation problem. If the left grip screws are not tight the same result can occur.

Next, the trigger's pretravel screw has to be affixed with blue Loctite sealant to prevent traveling under recoil. If its not, then it will change location and that can affect the operation of the disconnector. The result is a trigger that feels like it is not connected to anything when you squeeze it.

R,
Bullseye

Update:
First, thanks for the interest and responses to my post.
As it turns out the bolt was not locked at all. I’m embarrassed to say that in my anxiety not to force anything I was just simply not applying enough muscle. The ‘smith did some polishing and smoothing of the relation of the new hammer bushing and disconnector plus we had to experiment a little with the pre-travel and over-travel screws but I’m happy to say that now all is well. I tested it today and it performed flawlessly.

THanks again for the interest

Great to hear that it is all working now. Those screw positions are critical. What usually gets someone into trouble is setting them "too perfect" which results in a non firing firearm. There has to be a little slack to allow for the disconnector to reset on the sear and to prevent the sear face from dragging on the hammer after let-off causing a light strike.

R,
Bullseye