I have a Colt Lightweight Sporter bought around 1992. It has the strange half cut up bolt, blocked lower and the large front disassembly pin.

I would like to switch to a flat top receiver so I can mount a nice Aimpoint on it correctly. I was thinking of doing this myself.

What receiver would work with this rifle?

Do I also need a rail hand guard to get an Aimpoint in the correct location? I keep seeing pictures of the back of the Aimpoint even with the back of the ejection port. Is this correct?

How much do you want to spend?

Regards,
Gary

Daniel Defense big hole upper flat top
imo

Quoted: Daniel Defense big hole upper flat top imo

Bingo

The Daniel Defense big hole upper flat top looks very interesting, but they don't have much info about it on their site.  Do many members here have them?

Is $225 usual for upper receivers?

This part make me wonder:
"Note: This product is currently out of stock. We are currently taking orders, the next available shipping date will be Sept. '03.

Will a regular upper receiver like a Bushmaster work with offset pins?

Yes it will work........

Quoted: Yes it will work........

Hmmmm.  Well that opens up a whole new world.