A common question that I have been getting is what is the small screw for that is seen on some of the Colt monolithic/modular upper receivers.
As a visual aid to those who aren't able to see a modified upper receiver in person, I did this short video. Let me know if you have additional questions in the comment section below.
I will redo this video at a later date now that I see the lighting self-adjusted alot.
![](https://i.ytimg.com/vi/CQU8F6aPnpQ/mqdefault.jpg)