Hello all, longtime lurker, and lover of the pew. I have built 2 AR15s and now want to build an AR9.

My parts so far:
McPherson billet dedicated AR9 lower (small outfit in NH)
Fire control group milspec (leftover from prior build)
7 inch Odin Works heavy barrel
VG6 Epsilon flash hider
KAW Valley Precision buffer kit with SS spring and 7.5 oz buffer

Have not picked an upper or BCG/CH as all I want are sold out, open to suggestions!
Thinking about Faxon nib BCG (14 oz)
FM upper
Radian Raptor CH.

And so now my question. I am trying to use takedown pins from another build, and noticed there are no holes for a retention spring and detent. So do I need specific Takedown pins?

I have added a few pics for good measure