I was never into AR-15s until I saw a guy shooting an AR pistol. It had a 7.5" barrel and was barking huge fireballs.
A month later, I was buying all the parts to assemble my first AR in my living room floor. This first build, I bought a stamped lower from Anderson Manufacturing, which was the cheapest part of the gun at $42. In these pics, it's got my first 80% lower from Thunder Tactical with a skeletonized mag well.
This is my most "Gucci" build, because in my research all the GunTubers said, "Make sure the gas system is all from one manufacturer." In 150 hours of research, Bravo Company Manufacturing (BCM) offered the best-built bolt carrier group on the market. They were the only ones shot-peen hardening their bolts, as well as using magnetic particle testing. So, the upper, BCG, barrel, tube, gas block, and charging handle were all BCM. I will never spend that kind of money on those parts again. Also, if you're looking to do a build, OdinWorks now makes bolts that are MPT.
Through talking to gun guys on the web, I quickly moved away from chambering the gun in the standard 0.223/5.56 caliber. 300BLK is designed to burn its powder in 9" and is readily available in subsonic and supersonic loads in a wide range of weights. So, the priorities for this build were 1. Reliability. 2. Running as silent as possible. 3. Concealable (backpack).
All in, this build was $3,500, including the silencer and tax stamp. The best investment I made was a JP Rifles "Silent Captured Buffer". I picked up an optional spring kit that allows you to tune the buffer. I fired a single subsonic round from it, looking for it to lock back on empty magazine until the spring tension wouldn't let it lock back. Then I backed it down to the last spring that worked.
That means the gun runs a little under-gassed (ejection pattern) with subsonics and no suppressor. With the silencer, it runs like it's properly gassed with subs. Running supersonics it ejects as if it's slightly over-gassed.
It's a little louder than a pellet gun, and it fits into a backpack. I can assemble or disassemble in under 20 seconds, and easily carry 4 full magazines in the pack. I picked up a 18" x 18" welders blanket rated to 1,200 degrees and it lines an inner pocket perfectly. So, I can drop a hot silencer if the I'm in a hurry.