A few weeks ago, I was working on an AR-15 lower receiver. It was an 80% lower that I had done the milling on. I found a hole in the lower not wide enought for the detent pin and spring. I believed it was just some paint or other defect obstructing the install. I decided to drill it out really quick, well the bit stuck and snapped off. This hole was to retain the rear receiver pin. The broken bit was t large to be pushed out and I did not want to scrape a lower I had spent the time and money on. I ended up finding a chemical solution to the problem. I read that you could heat up water to boiling and pour as much Alum into it as would not render the solution insoluble.
NOTE - You need to make sure you use a pot that is made of aluminum, glass, pyrex etc. DO NOT use a steel pot.
I purchased this pot:
https://www.amazon.com/gp/product/B009NFAI82/ref=oh_aui_detailpage_o08_s00?ie=UTF8&psc=1
and 1 lb of Alum (aluminum sulfate):
https://www.amazon.com/gp/product/B00016Q6BK/ref=oh_aui_detailpage_o08_s00?ie=UTF8&psc=1
I then filled the pot with about 2 liters of water (just enough to cover the hole and stuck bit). Set a stove top burner to high and once the water started to boil I added the Alum a bit at a time until I had dissolved the whole LB into it over the course of 30 - 60 minutes. After you start adding the alum eventually you will see the chemical reaction occur, bubbles were actually coming out of the hole in the lower with the stuck bit. I then had the burner on for about 8 or 9 hours on high. Checking in on it here and there. Well I turned it off for the night and wanted to check the progress so I took a look and low and behold the bit was nothing but residue in the whole. I just cleaned it out with a pipe cleaner and it was ready to go. NOTE this process DID remove the anodizing on the outside of my lower
I hope to update this when I get some more time with photos and videos of the process.
NOTE - You need to make sure you use a pot that is made of aluminum, glass, pyrex etc. DO NOT use a steel pot.
I purchased this pot:
https://www.amazon.com/gp/product/B009NFAI82/ref=oh_aui_detailpage_o08_s00?ie=UTF8&psc=1
and 1 lb of Alum (aluminum sulfate):
https://www.amazon.com/gp/product/B00016Q6BK/ref=oh_aui_detailpage_o08_s00?ie=UTF8&psc=1
I then filled the pot with about 2 liters of water (just enough to cover the hole and stuck bit). Set a stove top burner to high and once the water started to boil I added the Alum a bit at a time until I had dissolved the whole LB into it over the course of 30 - 60 minutes. After you start adding the alum eventually you will see the chemical reaction occur, bubbles were actually coming out of the hole in the lower with the stuck bit. I then had the burner on for about 8 or 9 hours on high. Checking in on it here and there. Well I turned it off for the night and wanted to check the progress so I took a look and low and behold the bit was nothing but residue in the whole. I just cleaned it out with a pipe cleaner and it was ready to go. NOTE this process DID remove the anodizing on the outside of my lower
I hope to update this when I get some more time with photos and videos of the process.
