Advice Needed on M16 where Semi Auto Position does not work correctly

[Greasegunner]

Hello All, I own a M16 which works on Full Auto, and safe but not Semi.

In semi when i pull the trigger, only one round goes off but when i let off the trigger,

instead of the click you hear when it resets, it drops the hammer and fires again.

I have replaced the disconnector and the disconnector spring.

Can someone troble shoot it for me?

Thanks

Haris

Edited June 4 by Greasegunner

[WB1775]

Sounds like there is an issue with the Sear or sear connection on the Trigger/Hammer not engaging in semi when you release the trigger, operating almost like a binary trigger setup.  I would remove the Trigger and hammer and check the sear engagement points.

[MPFiveO]

I would replace the entire fire control group, new hammer, trigger, disconnector and springs.

It's possible that the hammer and or trigger pin holes have become worn to the point that the receiver is out of spec, but hopefully this isn't the case.

Another possible culprit is a broken hammer pin. That will allow enough movement for the hammer to slip off of the disconnector. It will also damage the receiver if not fixed quickly.

Feel free to reach out to me if you want to swap pictures via text. I've been working on M16's for 35 years.

Also, I have a Ingram M6 magazine if you're still looking for one.

[Greasegunner]

thanks a lot

will swap out

[gftiv]

Fire control groups are finicky. Is your receiver GI spec? If not, your fire control may need to be modified to your specific receiver. If your receiver is GI spec, try some GI spec fire control parts. this may help.

I have had to modify my fire control group on my non GI spec receiver.

[Greasegunner]

On 6/4/2025 at 6:07 PM, MPFiveO said:

I would replace the entire fire control group, new hammer, trigger, disconnector and springs.

It's possible that the hammer and or trigger pin holes have become worn to the point that the receiver is out of spec, but hopefully this isn't the case.

Another possible culprit is a broken hammer pin. That will allow enough movement for the hammer to slip off of the disconnector. It will also damage the receiver if not fixed quickly.

Feel free to reach out to me if you want to swap pictures via text. I've been working on M16's for 35 years.

Also, I have a Ingram M6 magazine if you're still looking for one.

I took your advice and now its runs as it

should

Thanks

GG

[MPFiveO]

As Hannibal Smith used to say, "I love it when a plan comes together"