All AR parts are universally interchangeable. Go for it.
Yup, mix n match uppers and lowers at will. (just don’t shoot Will)
That’s what I thought but needed to get advice so that I don’t make my usual mistake of jumping before looking carefully.;-)
With the exception of Colt and their idiot large pin receivers. But that only affects the trigger group I believe. Eithe rpin size is readkily available, so no worries there. No one buy Colt lowers anyway.
This is all true for the small caliber (.223/5.56 NATO) AR series. When you get into the big stuf (.308/7.62 NATO) things get a bit murkier but still manageable.
Not quite. I've made my own from kits, but there are issues with fit. Not usually bad, but you will often get less than a tight fit of upper and lower.
This is fixable by:
1. not carring about accuracy.
2. fitting a shim in front of the mag well
3. using an oversized or sleeve shimmed pin
4. redrilling the hinge pin holes and using an oversized pin
I have found #2 to be cheap and easy.