Assembling 80% Lower and testing

[AirBoss]

I was able to mill and later assemble 80% polymer lower.

I'm testing my trigger group and hammer assy. Here is what is going on:

1. All trigger and hammer assemblies installed in a lower
2. I cock the hammer using thumb
3. I squeeze my trigger and hammer falls forward
4. I keep my trigger squeezed
5. while keeping trigger in the rearward position, I cock the hammer using my thumb. The hammer locks.
5. As soon as I release my trigger, hammer gets released all the way forward.

Setup was working fine before I lubricated some points in the trigger group.

What could I have done wrong?

How can I fix this behavior?

[phsieh10]

Disconnect spring is in backwards. Fat side goes into trigger.

[AirBoss]

Thanks for suggestion. I checked all of the springs in the trigger group and all were in the right orientation.

Just as a precaution, I pulled the disconnector spring to increase tension.

I re-assembled whole trigger pocket and now it is working fine.

I researched online and some people suggested removing material from the disconnector forward area.

Any other suggestions to prevent it in future.

[VytamenC Tactical]

could have a out of spec hammer, trigger disconnector part or you were using a jig without drill bushings and walked either a hammer pin hole or a trigger pin hole. throw another fire control group from another working gun in the lower see if it works correctly. re evaluate from there. you either have a bad lower or a bad fire control group

[ar15barrels]

What you have is a LACK of disconnector engagement.
This can be from bad parts or from the pin holes being located wrong.
If the pins are not in the correct locations, the parts behave differently.

JP's gunsmith-fit trigger instructions give a good explanation of disconnector timing and how it should be working and how to correct it if it's not.

[AirBoss]

Thank you ar15barrels and VytamenC Tactical.

I have replaced FCG and it works fine.