I had an AR build come across the workbench. The owner bought it from the guy who built it. I’m not sure when it was built but apparently it didn’t run.
![](https://john1911.com/wp-content/uploads/2019/01/Upsidedown-Gas-Block-ar-rifle.jpeg)
Upon first inspection I easily found that the buffer retention pin was missing. The first fix on this rifle is installing the missing pin.
After installing the buffer retention spring and pin I went to work inspecting the rifle. After a quick glance at the BCG just to make sure that was in order, I went to the inspect the gas block.
In the picture you will notice the bi-pod mounted to a rail on the bottom of the gas block. It took all of a couple seconds to realize that the rail should have been on top of the gas block.
Someone had decided to rotate the gas block 180 degrees so the bi-pod would work. The only problem with that is, by doing so they turned their AR into a single shot rifle.
![](https://john1911.com/wp-content/uploads/2019/01/Upsidedown-Gas-Block-gasblock2.jpeg)
I removed the gas block and hand guard to make sure the gas tube wasn’t damaged since it got a bit twisted during the rotation.
When everything checked out. I reassembled the rifle properly and test fired it.
![](https://john1911.com/wp-content/uploads/2019/01/Upsidedown-Gas-Block-20190116_133428.jpg)
No more issues.
The buffer and spring don’t pop out when you break it down and the rifle runs like it should. It turns out this was just a rookie mistake by someone not familiar with how a DI system works. All in all a super easy fix.
Freeze
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