Re: First AR-15 build Q's
When you roll your own, YOU are now the QC department if building the upper assembly and lower receiver group.
If you plan on shooting it regulalry and expect it to go bang reliably, biggest things to focus on are:
Quality barrel with identifiable chamber of your desire, good steel, correct gas port diameter for gas system length, good crown.
Quality bolt made from tool steel alloy, with a QC process that is equal to the Milspec if you agree that HPT and MPI are good things. I've had excellent results with BCM bolts, Colt bolts, Armalite bolts, WMD Guns NiB bolts, & certain chromed bolts. I've gotten great use out of J&T bolts but reached a breaking point at the cam pin hole at over 10,000rds of high-volume shooting, which is expected when you torture the gun on non HPT/MPI units, althoug they may break as well.
A lot of people make blanket suggestions about extractor buffers, certain springs, and such, but what I've seen is that the extractor and ejector assemblies need to be sorted with quality components, and balanced with each other. Often, the D-fender extractor spring buffer will provide way too much extractor power, and makes it more difficult for the blaster to chamber with unnecessary tension required to snap over the cartridge rim.
Bolt carrier. I prefer to use M16 carriers, with a Milspec chrome-lined and hardened key attached using Permatex or red loctite after degreasing. I like US-made fasteners, not "YFS" Taiwanese units, torqued to 35-40 inch pounds, with Loc-tite in the fastener threads, then staked with a dedicated compression tool, not peening in a vice, since peening can blow your fasteners and seal. This is a critical area of the DI gas system, and a lot of companies have skimped on the Permatex sealant, as they didn't even know about it.
So the basic core stress parts of the carbine/rifle are the heart I focus on first.
Then I move to the recoil system and match it to the gas system. It's a balancing act of dwell time, port diameter, what kind of lock time I want, so I actually take several buffer weights to the range when I test-fire. The 16" legal barrel/Carbine-Length Gas System can pose a lot of problems with 2.9oz buffers, but generally works with 55gr ammo and a smaller gas port diameter. I prefer H2 and H3 buffers for different configurations, especially when we start talking about different calibers.
Quality Chrome Silicon springs have great life to them, but you need to measure your recoil spring every 2,000-4,000rds to see if it needs replacement if you shoout high-volume. If you just plink a few rounds, it won't matter much.
Then you can start looking at what receivers you're using, lower parts kits (not all are created equal), and furniture.
BCM complete uppers are excellent if you want to play it safe on your first AR. Order from them with confidence.
There is a wealth of build guide info from mostly reputable people on youtube, like Brownell's.
Good luck with your project. It's a fun hobby to have.
