Now I know why some people don't understand the difficulty with front pivot pin installation. I built a lower for a friend the other day and the detent spring was quite a bit shorter than I'm used to, the pivot popped right in, no special tools, no razor balde, no allen wrench---pop...it went right in. It retains the front pivot pin as it should. So, moral of the story: If the spring is about a 1/16" below the hole, the front pivot pin will pop right in....hmmmm. As long as there is enough spring tension to allow the detent to retain the pin--you're home free. On my last 3 lowers, the detent spring was about 1/16" above the hole, and I had to wrassle those b@stards good to get them in.

Next build I'll know.....

That's the way mine was, I had to depress the spring about 1/16" to be flush, then get the detent in too. It's not easy. Yeah, I wondered why it had that much tension, it shouldn't need it. If I could have dropped the detent into the hole a little it would have been pretty easy.

My friends spring had about 1/4 of the detent sitting in the lower, I just pushed it down with the pivot pin, spun it around, and "click" there it was. Took 2 seconds. I laughed as I remembered hunting down my detent 3 times in the garage....

That why you use a drill bit to check the hole first.... make sure it is clear of debris.... then clip coils on the spring until it is just 1/16" or so short of the hole.  Makes quick work.

Oh, sure...now you tell me.

Yeah me too. You could have talked about that Moday, the day before I built my lower.

Some things.... are MEANT to be learned the hard way.  It's called experience.