Re: 4.00" OAL extended magazine. DIY?
It's done all the time. A stripped receiver or a barrel blank is not a firearm. Raw bolt rifle parts don't even look like a gun. A high school student probably couldn't bring it in but when the metal shop teacher is approached by an adult with a little one off project they will usually bend over backwards to help a guy out. Common sense says leave it in the car until you get approval from the teacher.
When my son was taking the machine shop program at both the high school and then later college he did gun part projects all the time. He was fitting barrels and muzzle brakes at the college. We still have the working cannons he built in 2009.
The college machine shop teacher also frequents our shop and Brady still volunteers on their shop night. He says other guys are bringing in gun parts all the time.
Right now the class project is billet AR lowers on the schools CNC.
Some kids want to be a fireman or a doctor to help people. I wanted to be a gunsmith.
NRA Life Member and I vote.
Only accurate rifles are interesting.
Gordy and Brady.