It's generally my opinion that gaps should never be covered..
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It's generally my opinion that gaps should never be covered..
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Punches, castle nut wrench, barrel nut wrench, vise, vise blocks, gauges (including headspace), torque wrench. Sure you can go cheap on these, but we’re talking best practices.Originally Posted by Red*Lion
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I have a few scattered thoughts:
-Let people know how much experience you have so we can guide you better
-Just because you know a buddy who can square your upper receiver face doesn't mean you should
-You might consider building the lower as an A5
-Grease, properly torque, and stake your receiver extension assembly. Be sure it's 7075.
-A CMMG LPK is adequate. Their pistol grip sucks. Their triggers are great for a mil-spec.
-Just buy a complete BCM upper (I can build uppers but I can't build one as nice as a factory BCM upper). Insert high quality BCG and 7075 charging handle.
-Consider a Geissele optic mount instead of QD.
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Lots of folks will say just buy from a high quality manufacturer instead of build. This used to frustrate me because it didn’t answer the question (if we are specifically talking about building then “buy an XXXX” doesn’t answer how to actually do the build correctly to end up with a reliable rifle), but I have come to understand that others say this because of all the little checks and gauges that a manufacturer would be doing to ensure reliable functioning. Plus it becomes a statistical situation- you can be more confident in the repeated reliability of thousands of rifles built by a highly regarded company vs. the statistical reliability of 1 rifle built at home. That said, can we lay out what would actually need to be done to complete a good quality build and let the OP decide for himself if he is willing to invest the time, money, and effort?
My opinion is that I believe a reliable rifle can be assembled with the proper parts, tools, and attention to detail. It just depends how much time and effort you are willing to put into it. Below is just a summary of some of what I’ve learned from others over the past several months:
Use multiple forums and search for threads around reliability, home builds, frankenguns, quality AR, and any other term you can think of. I have found all of the below helpful to one extent or another:
M4carbine.net (obviously)
AR15.com
Primary and Secondary
Pistol-Forum (they have a sub category for carbines)
There are some great threads on all of these about build quality, home builds that work and don’t work, what parts commonly break during carbine courses, observations from high round count hard use (thousands upon thousands of rounds on full auto), and more. These can provide great insights into what makes an AR reliable.
Buy quality parts and tools. Example regarding tools; I have seen 3 different sizes of 1/16 in. roll pin punches. 1/16 (1.5mm), 1/16 (1.6mm), and a 1/16 from Home Depot that is bigger than both of those. An oversized roll pin punch will get stuck in your roll pin hole, trust me I’ve made that mistake. Using the correct tools of good quality and using them the correct way seems to make building more fun, more enjoyable, and results in more confidence in the rifle in my opinion.
For examples on parts, metal injection molding (MIM) are considered lower quality than cast parts. There are varying degrees of carrier gas key staking quality, some low quality bolts seem to break fairly quickly, higher quality last a lot longer. Even subtle variations in parts, for example the beveling on the end of the gas tube that goes into the gas key, play a role In reliability. Searching the threads for others experiences is your friend when looking for quality parts. Even parts as small as the extractor spring can affect reliability. The buffer spring is also commonly mentioned as being critical to reliability and should be of high quality. I recommend buying from manufacturers or distributors with good customer service and warranty reputations. If you get a lemon or parts are missing a company with a good reputation will replace it no problem.
Some of the small details about how the rifle is assembled can matter just as much as the parts:
Muzzle device properly torqued
Gas block properly aligned to gas port.
Gas tube properly aligned to carrier key.
Gas block properly attached.
Gas port hole is the proper dimensions.
Molybdenum grease or aeroshell grease on the proper areas.
Proper staking on gas key screws and castle nut.
Proper torque on barrel nut.
Verifying feed ramp alignment.
Proper buffer weight.
Proper buffer spring length.
High quality ammunition and magazines are also commonly referenced as critical to reliability.
Some of the checks and gauges:
Gauge gas port size.
Gauge head space.
Gauge firing pin protrusion.
Checking gas ring seal.
Checking if extractor or other bolt parts have become magnetized.
SOTAR even has gauges for gas key and gas tube, and I think firing pin hole on the bolt.
I’ve seen a video of SOLGW using a special go/no go gauge to confirm inside diameter of their low profile gas blocks.
There are also considerations to be made regarding the tolerances of parts from different manufacturers and how they fit together. To my understanding if two parts are made to the opposite ends of the allowable tolerance range they may not fit together or function as ideally as intended, or maybe not at all.
The more of the little details like the ones above that you can check off the more confident you can be in the reliability of the rifle you build. At the end of the day, you can do tons on research and put the time and effort into learning what makes the rifle function reliably, or you can slap parts together and hit the range. However, if you just slap parts together you may end up with a rifle that is dangerous, doesn’t work properly, or that doesn’t work at all.
It’s YOUR rifle, so ultimately it comes down to how confident YOU are that it will work when you need it, and how confident YOU are in your skills to use it when you need it.
I also suggest function checking as you build, don’t wait until the end. As you should with any defensive firearm, test with the ammo you intent to use in at the range before betting your life on it.
Best of luck!
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Great advice. I would never discourage a personal build/craft, However:
- A lot can go wrong with a home build: the list is virtually endless. Last year a kid showed up to a training event I attended with a home build and he had a catastrophic malfunction due to several build screw-ups. He noted the carbine was a home defense build...
- You need a lot of tools to build an AR right: and possibly specialty tools to diagnose any number of potential build tolerance issues. I have lost track how much I have invested in my tool kit?
- You need specialized knowledge to build/assemble an AR right and an understanding of the process to modify the gun. It's a challenge even for experienced enthusiasts: even professionals struggle at times to diagnose factory issues, especially bubba'd guns.
Quality manufacturers have done years of product evolution and invested a significant amount of resources into solving problems. I prefer the military manufacturers myself: at the very least some military contract heritage, and then also duty purposed guns are another thing I look for. And if you are on a tight budget you can really do well with PSA premium line and a few modifications.
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agree
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Hey thanks everyone for all the input and I'm sorry to make a post then ditch out for so long. I've been extremely busy at work. Anyhow, after reading what everyone has said I have decided to keep the Aero UPPER/LOWER but I'm going to put that on hold for more of a range gun. To answer the question, No, I do not have very much experience building AR's. I've done simple things like install a mag release and change pistol grips but never a complete build and I don't have many tools. I feel my knowledge level is pretty high but I don't have the hands on as of now. With all that being said I've decided to follow alot of your guys advice and buy a complete lower and a complete upper. I'd buy a rifle but the funds are a little tight. I've decided to go with a complete BCM or Centurion lower. Problem is I can't find either anywhere. I do however have a lead on a take off colt le6920 complete lower for $400.
What do you guys think about a complete Colt lower with say a BCM or Centurion complete upper? Or maybe just buy a 6920 upper which there are some in stock at various places with a Colt BCG though it may not be when I have the funds in a few wees.
Last edited by Cowboys1; 11-21-20 at 21:01.
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If an upper doesn’t work well with a Colt lower, then the upper is the problem. Really can’t beat a Colt upper, either, even if there are “cooler” uppers out there these days.
So you should be good. Just from my perspective, $400 is a bit high for a used complete lower of any stripe, but it is what it is. Hold out for a few days, some companies may have stock held back for Black Friday.
“God doesn’t need your good works, but your neighbor does.” - Luther
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I think it's just a take off but not actually used. I'll call them tmrw to verify.
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go with the colt lower all day everyday
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