AR-15 SP1 issue

[Tony Wells]

Got handed a little project today. I have a Colt AR-15 SP1, which is the "slick-side" or "slab side" lower receiver. I have a .22 cal upper, and a .223 upper for it. The lower receiver has the front pivot pin hole in the large option, I believe .3125 (not actually measured it yet). The .223 upper matches it, but the .22 upper has the small front pivot pin. I don't want to have two pins, and I know there are offset pins for this, but I am thinking of reaming or boring the pivot pin hole in the .22 upper to accept the same pin as the .223. That would be the 5/16" pin.

Anyone see a problem doing this? It appears that there is sufficient material to be safe and strong.

 

[Highpower]

I don't see any problem with it.

I've got an old slab side Colt Sporter II with the large pin (.315). I still curse Colt for inflicting that on us mere mortals to this day, but I digress.....
I used to have a dedicated RF upper for it, but no longer. Still have the offset pivot pin though.

 

[Tony Wells]

Yep, a pox on Colt for that. Something I read suggested that it was an effort to discourage military hardware from getting to the civilians. Dunno bout that, but it is a popular topic on the AR forums.

Thanks Willie.

 

[Highpower]

Yeah. Got the stinking large trigger and hammer pins too.

But I do loves me AR's though.