I have had my FAL for 10 years now and the whole time the last round bolt hold open has not worked. I knew the pin had been ground off and I figured I'd need to buy a surplus hold open but I just never "got around to it".
Well I stumbled across this article
yesterday. So... a trip to the deep-o and a few minutes with a couple of hand tools and vee-oh-la, working last round bolt hold open.
Two things that don't seem right in the article:
1 - The actual roll pin diameter you need is 3/32.
2 - There is no need to remove the hinge pin. Just make sure it's unloaded and the bolt is forward.
The deep-o only had 3/4 length so I had to cut it to size. I suggest cutting it a little long and then grinding it down as needed.
And remember, roll pins are not all created equal. You'll want one that's a bit larger than 3/32. The first couple I tried were too small. You will know it's too small if you can push it all the way through by hand. I found one that would go in the larger hole but wouldn't go through the smaller.
Don't move the mag release once the pivot pin/screw is removed and it should stay in place. The bolt hold open will slide out the bottom.
Roll pin installed and ready to go back together. In order to get the pivot pin back in you have to position the bolt hold open about 1/4 inch from the bottom of the slot.