I put together rifle with a brownells 601 upper and lower a few years ago. Quickly realized I didn’t like the 601 upper throwing brass in my teeth shooting lefty. I swapped the 601 (slick side) upper for a C7 (has brass deflector)

The 601 receiver set uses a takedown pin with a ball detent  that snaps into a counterbore that’s in the upper and lower (maybe just the upper I haven’t looked a it in a while)

The C7 upper obviously doesn’t have this area machined out so nothing captures the ball detent so the takedown pin isn’t secured.

Should I just get one of those Colt two piece front takedown pins?

We’re the two piece takedown pins standard diameter?

The Colt two piece is going to measure .312. A standard lower is .250 I just had 2 Unique, LLC in Windham, ME turn me two front pivot pins to .250

Before


After


After refinishing with Birchwood Casey

Colt produced a .250” diameter, two-piece pivot pin in relatively recent times, but I’m not sure how common they are, or where to find one at the moment.

Okay, this is something I hadn't thought of before...

Let's say I had an NDS-605 upper, that I was planning on putting on an H&R 601 lower when those are out...  so, that upper would need to be modified to work with a 601 pivot pin?

Of course they do, cause you guys are awesome.  

Thanks for the reply.

^This