Metal all the way. More durable and saleable later on.
Aluminum most definitely, but at the same time with the lower price of receivers it is not worth it to me to buy a 80% lower.
Correct me if I am wrong, but once you make an 80 percent complete or even 81 percent, you can no longer sell it unless you have a manufacturing FFL.Metal all the way. More durable and saleable later on.
Never seen a law forbiding selling a homebuilt firearm therefore one can assume its not a problem to sell a homebuilt firearm. I have read in 27 CFR 478.92 that firearms for sale must be serialized. IANAL YMMV