Quote Originally Posted by everready73 View Post
San tan had really nice receiver sets. Mega was bought out by ZEV but you should still be able to find mega sets or the ZEV are good to go as well.

I agree with all the other suggestions to go with Sionics NP3 BCG if you want a coated BCG. Nickel Teflon is good stuff.

As far as lower parts kits Sionics, Colt, BCM are good choices. Get a builder set and add the trigger and grip of your choice.

Vltor A5 buffer system would also be worth a look over standard carbine
I have a San Tan build, it's nice but a bit heavy duty. The ambi controls are also nice but a bit bulky and proprietary so hope they don't break. There are some fiddly bits in the upper receiver to "tune" the fit which I did not need to use. Radian has San Tan or the same company do their receivers too as they appear identical.
If I had to do it over again, I'd probably pick up a PWS ambi receiver set with the Lightweight upper.