View Full Version : CNC Machining, QA/QC, And the World of Good Enough
noonesshowmonkey
12-08-16, 15:49
The recent threads about two different rifles of two different price points being put through the ringer brought up--to my mind at least--the issue of how the modern manufacturing era that we currently live in and enjoy influences the quality, durability, and reliability of firearms.
To repost:
[The performance of a PSA rifle over 5k rounds] is a strong testament to the fact that CNC machining takes so much of the guesswork and feel out of building a firearm, and exposes the genius of the AR-15 pattern: that it is a series of parts which, when made to specifications, can be assembled and built and function. The only significant variable--when the manufacturer is producing mil-spec, within tolerance parts (which the above mentioned advances in high quality, high precision CNC machining makes far more reliable and easy)--is going to be QA/QC.
This is not to understate the value of QA/QC, or the smaller details that make up a KAC or DD or BCM rifle vs. that of PSA, but rather to solidify the notion that the AR-15 is an eminently producible firearm.
How much of this view is true? What are the realistic controls and acceptable variability of various CNC machining operations, and how do those compare to the operating tolerances of the AR-15? If a CAD guided 5-axis CNC machine can produce results to within the 10^-4m to 10^-5m with pretty incredible repeatability, and the specifications of those parts are clear and have been tested and are known to function (ie the TDP), then can't we expect just about any shop with a decent CNC machine to produce parts which are in spec, and thus functioning?
And if this is true, then where do we need to spend our time and our money? MPI testing seems a very worthy thing, as any high resolution imaging will show most (if not all) gross irregularities within the material itself. From there, the issue is mostly one of QA/QC: throwing a micrometer onto the part to ensure that it isn't irregular.
So, what are those parts which need the most attention? What are those parts for which there is absolutely no compromise?
Clearly, the Bolt Carrier Group is a strong candidate. The BCG already represents the least homogeneous part of the AR-15, the place where the largest variety of materials are present, where the vast majority of wear and tear occurs. Even so, if the correct materials are used, can we not produce a reliable BCG with a startling level reliability and repeatability?
Next, barrels. The barrel is probably the place on the AR-15 where the most amount of time, money, and effort should be spent, and I'll willingly cede the ground that whatever mixture of special sauce produces a sub-moa barrel is worth the investment, and that brand can mean a great deal here.
Past these two places, what are we buying but a few lumps of aluminium that have been CNC machined to nearly identical specifications, and produced at levels of precision far beyond the operating tolerances of the rifle itself?
The fact that both those threads were locked is evidence that some refuse to accept this reality. There is no "secret sauce" when it comes to building a servicable and reliable AR. With modern manufacturing, any company with the desire and commitment can put out a consistently functional rifle. Heck, there are guys milling their own lowers in their freaking garages that go onto run without any issues. Yet, some still would have us believe that companies, in spite of having the capital for precise production lines can't possibly get things right. And base the opinions solely upon the roll mark. Regardless of the progress we've seen, there are still many who claim that mfg A can do no wrong and mfg B can do no right.
We can't ignore that decisions are driven by cost, and some mfgs will find savings through departure from the mil-spec. But, does that really matter for things like barrel steel, linings, bcg material, etc? As long as the materials used were properly constructed and processed, it's generally meaningless.
Now, when we move beyond essential functionality and reliability, there are some who've found a better way; as you elude to with the sub-moa barrels. And that's what's truly great about the times we live in as AR owners. Overall, rifles have become so reliable that we can now nitpick at the little improvements we'd like to see. We all have different desires and opinions on what would make our specific rifles better, and are quite fortunate that there are so many options being produced to fill those demands.
Personally, I agree BCGs and Barrels are a good place to spend time and money. For me, triggers and coatings are others. Yet ammo is probably at the top of the list. At face value, because most rifles are generally reliable, we'd be best served to focus on practice and training. Tinkering with a rifle to improve its functionality is largely unnecessary, and is more about preference. Most would be much better served leaving the rifle alone, and instead work on improving the guy holding it. On a more technical note, in regards to ammo, there is always room for opportunity. Any round can reach out to 5-600 yards, but advancements can be made to increase the performance at those ranges. Better powders, projectiles, etc. Same goes for CQB applications; and everywhere in between. I'm sure others' desires will vary.
Eurodriver
12-08-16, 20:15
Sigh.
It has little to do with tooling.
It has little to do with materials.
It has even less to do with a chart.
It has everything to do with attention to detail. Everyone puts out a bad product once in a while, but not every company has a "where is my order" thread; not every company puts out canted FSBs; not every company sends parts kits out missing parts.
Some do. If you want to put your life in the hands of that company why on earth would you feel the need to get on the internet and brag that your life is worth less than the $500 it would cost you to go with a company that doesn't?
And If you say that your rifle isn't for those purposes, then you quite simply don't belong on M4C.
titsonritz
12-08-16, 20:26
It has everything to do with attention to detail. Everyone puts out a bad product once in a while, but not every company has a "where is my order" thread; not every company puts out canted FSBs; not every company sends parts kits out missing parts.
Not every company need BS parts (like relieved buffers or offset retainer pins) to compensate for their lack quality.
All other things being equal, assembly is the most important part of manufacturing. Period.
You can take a bunch of engine parts, kit them up so that they are identical in quality and config, and I'll guarantee you that a guy who builds engines professionally will get better results than a shade tree mech with a chiltons manual.
Most people who argue the "better than" or "just as good" angle have very little manufacturing knowledge, or they would understand this.
That's not to say that "vendor a" can't make a rifle the equal of "vendor b". But skilled, experienced labor costs more, and if you introduce non value-added steps like NDT and QA into the process, it drives the cost up. That's just a fact.
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Eurodriver
12-08-16, 20:39
All other things being equal, assembly is the most important part of manufacturing. Period.
You can take a bunch of engine parts, kit them up so that they are identical in quality and config, and I'll guarantee you that a guy who builds engines professionally will get better results than a shade tree mech with a chiltons manual.
Most people who argue the "better than" or "just as good" angle have very little manufacturing knowledge, or they would understand this.
That's not to say that "vendor a" can't make a rifle the equal of "vendor b". But skilled, experienced labor costs more, and if you introduce non value-added steps like NDT and QA into the process, it drives the cost up. That's just a fact.
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BUT THEY USE FN BARRELS
What "Good Enough" REALLY means is "Within Spec". If it's not within spec it's not good enough
Cost is
Raw materials
Chemistries
Tempers
Coatings
Proper dimensions
Proper use and knowledge of how parts interface to produce proper dimensions
Assembly
Qa/qc
What the specs allowed to go out the door.
Material tracking
1000 other influences.
You can dig deep into each category listed.
For instance, if your acid supplier is questionable, and sends you crap, and you don't check your stuff, you just made a bad batch of recievers. Will you scrap them? If you attempt to salvage, how do you ensure quality is kept? What methods are in place to ensure procedures are followed? On and on, this all adds cost.
The attention to detail the guy building in his garage has, is probably not the same as the guy building 100 rifles a day.
BUT THEY USE FN BARRELS
Lol....that they do. [emoji106]
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noonesshowmonkey
12-08-16, 22:49
You can take a bunch of engine parts, kit them up so that they are identical in quality and config, and I'll guarantee you that a guy who builds engines professionally will get better results than a shade tree mech with a chiltons manual.
Most people who argue the "better than" or "just as good" angle have very little manufacturing knowledge, or they would understand this.
As a man who has spent quite some time assembling / building in the aerospace industry, and then performing meticulous QA/QC, I can indeed understand and agree with this.
It has everything to do with attention to detail. Everyone puts out a bad product once in a while, but not every company has a "where is my order" thread; not every company puts out canted FSBs; not every company sends parts kits out missing parts.
Some do. If you want to put your life in the hands of that company why on earth would you feel the need to get on the internet and brag that your life is worth less than the $500 it would cost you to go with a company that doesn't?
This, and the above quote about assembly being crucial to the turning out of a good product, while very true, are not necessarily directly addressing my question re: the production of individual parts. At no point am I advocating for or against a given manufacturer, or a price point, nor am I attempting to create a false equality where there is none.
But, taken as individual parts, and simpler sub-systems (an assembled upper isn't exactly a demonstration of rocket surgery), parts produced out of known materials to known specs are, in point of fact, the same. The TDP defines the specifications, and those specifications have been proven to function reliably. If they call for 9130 or Carpenter 158 or 6061 or 7075 or 4150 or 4140 or if they call for balsa wood, those specifications, if met, produce a part that works.
Assembly is indeed where a great deal of voodoo comes into things. A BCG, for example, can be assembled or disassembled, with minimum handtools in a matter of minutes. There's a few pins, a couple of springs, some washers, and... well... that's just about it. Those are items that we know how to make, and have been making for years, and can now produce at tolerances far beyond what was available at the outset of the AR-15 pattern. There may be an art to staking, but there's a lot of mojo and voodoo and street magic used to describe hitting a punch with a hammer to displace some material. Maybe I am making light of the process because I've done it a few times, I don't know.
What "Good Enough" REALLY means is "Within Spec". If it's not within spec it's not good enough
This is, in fact, kind of my point.
SomeOtherGuy
12-08-16, 23:29
It has everything to do with attention to detail. Everyone puts out a bad product once in a while, but not every company has a "where is my order" thread; not every company puts out canted FSBs; not every company sends parts kits out missing parts.
This. Quality control costs money and requires good people (who also cost money). Anyone with a Mazak and a half-decent operator can machine approximately the same parts. So who will catch the parts that are out of spec or otherwise defective?
The farther you go in any profession, the more you will discover that common sense isn't, and simply getting the basics right puts you at a minimum of the 50th percentile, and often towards the 80th or 90th percentile.
Companies like DD, Colt, KAC etc are much much better at stacking tolerances. Others are not. The problem is not in one part of the manufacturing but the entire process as a whole.
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This. Quality control costs money and requires good people (who also cost money). Anyone with a Mazak and a half-decent operator can machine approximately the same parts. So who will catch the parts that are out of spec or otherwise defective?
The farther you go in any profession, the more you will discover that common sense isn't, and simply getting the basics right puts you at a minimum of the 50th percentile, and often towards the 80th or 90th percentile.
The person doing the work controls quality. the inspector can only assure the quality is there
Companies like DD, Colt, KAC etc are much much better at stacking tolerances. Others are not. The problem is not in one part of the manufacturing but the entire process as a whole.
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The AR is designed to to eliminate "tolerance stacking". It's designed so that when everything is made within tolerance, the parts will fit. If the parts of an AR don't fit or work together, something is out of tolerance
As a man who has spent quite some time assembling / building in the aerospace industry, and then performing meticulous QA/QC, I can indeed understand and agree with this.
This, and the above quote about assembly being crucial to the turning out of a good product, while very true, are not necessarily directly addressing my question re: the production of individual parts. At no point am I advocating for or against a given manufacturer, or a price point, nor am I attempting to create a false equality where there is none.
But, taken as individual parts, and simpler sub-systems (an assembled upper isn't exactly a demonstration of rocket surgery), parts produced out of known materials to known specs are, in point of fact, the same. The TDP defines the specifications, and those specifications have been proven to function reliably. If they call for 9130 or Carpenter 158 or 6061 or 7075 or 4150 or 4140 or if they call for balsa wood, those specifications, if met, produce a part that works.
Assembly is indeed where a great deal of voodoo comes into things. A BCG, for example, can be assembled or disassembled, with minimum handtools in a matter of minutes. There's a few pins, a couple of springs, some washers, and... well... that's just about it. Those are items that we know how to make, and have been making for years, and can now produce at tolerances far beyond what was available at the outset of the AR-15 pattern. There may be an art to staking, but there's a lot of mojo and voodoo and street magic used to describe hitting a punch with a hammer to displace some material. Maybe I am making light of the process because I've done it a few times, I don't know.
This is, in fact, kind of my point.
So what exactly is your question? You set the preface above but I dont see a question.
Going to OP, yes, all companies produce most of their parts within spec. Anyone can make a part within spec. It's doing it repeatedly and containing all that's not that is important and separates companies. I still don't think I answered your question though, did i?
The person doing the work controls quality. the inspector can only assure the quality is there
The AR is designed to to eliminate "tolerance stacking". It's designed so that when everything is made within tolerance, the parts will fit. If the parts of an AR don't fit or work together, something is out of tolerance
This is correct. Processes should be in control to the point that QA is unneeded, and a waste of money.
Tolerance stacking is resolved in the engineering phase. Companies that produce their own parts shouldn't experience it, and companies that use "bin parts" from another vendor most certainly will.
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There will be no problem with bin parts if those parts are made to spec. The AR really is a marvel of modern engineering and was far ahead of its time when it was developed. It's the first design to control headspacing to the point all bolts are a drop in fit with all barrel assemblies, a leap forward in rifle manufacturing. It's the first issue rifle to fully embrace modern production methods and it was readily adaptable to manufacturing control methods yet to be developed. That's it's real edge over the M14, AK, FAL and other designs
It has everything to do with attention to detail. Everyone puts out a bad product once in a while, but not every company has a "where is my order" thread; not every company puts out canted FSBs; not every company sends parts kits out missing parts.
That is ultimately the difference in ANY manufacturing environment. Anybody can produce a 1/100 or 1/1000 item but being detail oriented leads to consistency in producing a quality, functional product. When you have high quality processes that are detail oriented and consistently apply them the end result is that the 1/1000 item is the one that's low quality.
Generally in modern manufacturing 1/1000 is actually bad and you're shooting for the "6 sigma" solution in your statistical process control. That is there are 6 standard deviations between your mean output and the nearest specification limit. In a practical sense that means you produce <4 defects per million opportunities.
Scaling quality up to industrial scale is what separates the men from the boys.
Tolerance stacking is resolved in the engineering phase. Companies that produce their own parts shouldn't experience it, and companies that use "bin parts" from another vendor most certainly will.
I would agree that Eugene Stoner and everyone else that had a hand in developing the AR and the final TDP for our battle rifle strove to eliminate tolerance stacking. The weapon was designed to be mass produced with no final hand fitting of parts required.
Your statement - companies that produce their own parts shouldn't experience it, and companies that use "bin parts" from another vendor most certainly will - flies against the basic concept of mass production and the TDP. In an ideal system the parts flow into the assembly line just in time to be installed.
Generally those parts are manufactured by vendors with machines set up to manufacture those parts in high volume. Efficiency in production and cost is achieved by this small number of vendors specializing in the production of a greater number of the part than one individual manufacturer needs. Those shops should be more set up to ensure that tooling remains within spec as well as ensuring the raw material is as specified.
As an example of this I would invite you to run around Wichita, Kansas, and check out all the machine and instrumentation shops that exist along the periphery of the aircraft manufacturer's facilities.
In closing, do any of the AR producers make ALL their own parts?
I would agree that Eugene Stoner and everyone else that had a hand in developing the AR and the final TDP for our battle rifle strove to eliminate tolerance stacking. The weapon was designed to be mass produced with no final hand fitting of parts required.
Your statement - companies that produce their own parts shouldn't experience it, and companies that use "bin parts" from another vendor most certainly will - flies against the basic concept of mass production and the TDP. In an ideal system the parts flow into the assembly line just in time to be installed.
Generally those parts are manufactured by vendors with machines set up to manufacture those parts in high volume. Efficiency in production and cost is achieved by this small number of vendors specializing in the production of a greater number of the part than one individual manufacturer needs. Those shops should be more set up to ensure that tooling remains within spec as well as ensuring the raw material is as specified.
As an example of this I would invite you to run around Wichita, Kansas, and check out all the machine and instrumentation shops that exist along the periphery of the aircraft manufacturer's facilities.
In closing, do any of the AR producers make ALL their own parts?
I'm well aware of manufacturing processes and JIT. If a part is designed with tolerances that will work with other parts, and those parts are in spec, then tolerance stacking should not occur. It's when you get companies using parts--the manufacture of which they have no control over--from vendors, that you start seeing that.
The company I work for, we make everything but the coil steel the products are made from. Whether that steel is used for a product that is rolled, formed, stamped, welded, or machined...we are in control of its design and manufacture. That includes the engineering and design where the tolerances are spec'd. Therefore, if parts are in spec, they won't stack.
My Division, which I am the manager of, has over 32,000 active part numbers. If we have issues with any of them, they are NCR'd back upstream.
On the occasion we use vendor stuff, it is still designed and spec'd by us.
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There will be no problem with bin parts if those parts are made to spec. The AR really is a marvel of modern engineering and was far ahead of its time when it was developed. It's the first design to control headspacing to the point all bolts are a drop in fit with all barrel assemblies, a leap forward in rifle manufacturing. It's the first issue rifle to fully embrace modern production methods and it was readily adaptable to manufacturing control methods yet to be developed. That's it's real edge over the M14, AK, FAL and other designs
Fair enough, parts that are in spec should always work. I'm just not comfortable that all assemblers ensure that.
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Colt's TDP is intellectual property allowing them to mass produce AR platform rifles and carbines to meet agreed upon specs. Colt claims that their product can not be reverse engineered. The TDP also addresses parts manufacturing, of course. The TDP is all about mass production.
I'm not qualified to say much except that I have been studying AR technical topics and agree with Eurodriver, who pointed out that attention to detail in assembly is essential.
Fair enough, parts that are in spec should always work. I'm just not comfortable that all assemblers ensure that.
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That is exactly what sets companies apart. Both parts and methods of assembly have a specification. If you adhere to those, you will never have a problem.
There will be no problem with bin parts if those parts are made to spec. The AR really is a marvel of modern engineering and was far ahead of its time when it was developed. It's the first design to control headspacing to the point all bolts are a drop in fit with all barrel assemblies, a leap forward in rifle manufacturing. It's the first issue rifle to fully embrace modern production methods and it was readily adaptable to manufacturing control methods yet to be developed. That's it's real edge over the M14, AK, FAL and other designs
Yes and no.
There have been millions of AKs made in dozens of countries -- lots of potential for variation. The FN FAL was adopted and manufactured world-wide in non-Com-bloc states. Barring Metric-Standard conflict major components are supposed to swap.
In a perfect world components will be interchangeable. In practice, not so much.
Parts built to spec are inter-changeable. An M16 made in Canada, Singapore, the Philippines, or Korea works with parts made in Connecticut or South Carolina.
noonesshowmonkey
12-11-16, 12:17
Parts built to spec are inter-changeable. An M16 made in Canada, Singapore, the Philippines, or Korea works with parts made in Connecticut or South Carolina.
This is, overwhelmingly, my experience.
So, to my original question: what are we buying but a few lumps of aluminium that have been CNC machined to nearly identical specifications, and produced at levels of precision far beyond the operating tolerances of the rifle itself?
I'll agree that when buying a complete rifle, or even sub-assemblies like (especially, due to it carrying the barrel) an upper receiver or a lower, buying from a company that has rigorous QA/QC combined with well paid, knowledgeable technicians is worth the money.
I buy materials and features, not brands. Sabatier turns out a beautiful knife. I don't buy them due to their brand name, I buy them because they are the combination of materials, features, process, form and function.
In the case of the AR-15, especially as we stick close to 'mil-spec', the vanilla M4/M16/AR-15, most of (if not all) of the above variables are held as constants. We have a clear pattern, a clear specification, that determines what the product is. If parts are being produced within specification, which with the state of CNC machining these days is essentially a given, they (should) be functionally identical but for branding. The assembly of those parts may vary significantly from one shop to another.
Outside of other features, such as a fully ambidextrous lower, or lighteneing, or 'enhanced' BCGs, or any of the many other tinkereings with the AR pattern, the specifications are known to function when used in total.
This concept seems to bear fruit in conventional wisdom: do we not know to invest in the barrel, the trigger, and the optic? Those places with the largest functional variability?
There seems to be a wide choice of barrels. What are the criteria? About chrome plating, does it make a lesser quality barrel a better barrel? How much more cost does the plating process add?
It's like everything else talked about -- what was the quality of the barrel before plating? How was plating applied? How thick was it applied? Was it treated afterward to avoid hydrogen embrittlement?
Send a shit barrel to an aerospace plater and you get a shit barrel with a space-age coating. Send a hand-cut barrel to a bumper plater and you get a gnat's ass-tube that peels and cracks.
As we've pointed out before, the drawings and materials lists state what the customer wants. The mil-spec states what minimum inspection and function-test criteria an item must pass.
If a commercial source doesn't do batch or sample tests they should have a good return policy.
This is, overwhelmingly, my experience.
So, to my original question: what are we buying but a few lumps of aluminium that have been CNC machined to nearly identical specifications, and produced at levels of precision far beyond the operating tolerances of the rifle itself?
I'll agree that when buying a complete rifle, or even sub-assemblies like (especially, due to it carrying the barrel) an upper receiver or a lower, buying from a company that has rigorous QA/QC combined with well paid, knowledgeable technicians is worth the money.
I buy materials and features, not brands. Sabatier turns out a beautiful knife. I don't buy them due to their brand name, I buy them because they are the combination of materials, features, process, form and function.
In the case of the AR-15, especially as we stick close to 'mil-spec', the vanilla M4/M16/AR-15, most of (if not all) of the above variables are held as constants. We have a clear pattern, a clear specification, that determines what the product is. If parts are being produced within specification, which with the state of CNC machining these days is essentially a given, they (should) be functionally identical but for branding. The assembly of those parts may vary significantly from one shop to another.
Outside of other features, such as a fully ambidextrous lower, or lighteneing, or 'enhanced' BCGs, or any of the many other tinkereings with the AR pattern, the specifications are known to function when used in total.
This concept seems to bear fruit in conventional wisdom: do we not know to invest in the barrel, the trigger, and the optic? Those places with the largest functional variability?
You are assuming what is going into the cnc is perfect, and that the cnc is perfect, and that nothing happens to it between manufacturing the part and reaching the customer. None of those are true, and all offer an opportunity to deviate from the spec.
If it was all as simple as inputting the data into a CNC machine, and trusting the technology, there wouldn't be a need for offset buffer retainers.
As seen here: https://www.m4carbine.net/showthread.php?187098-Does-this-look-like-normal-buffer-wear
All other things being equal, assembly is the most important part of manufacturing. Period.
You can take a bunch of engine parts, kit them up so that they are identical in quality and config, and I'll guarantee you that a guy who builds engines professionally will get better results than a shade tree mech with a chiltons manual.
Most people who argue the "better than" or "just as good" angle have very little manufacturing knowledge, or they would understand this.
That's not to say that "vendor a" can't make a rifle the equal of "vendor b". But skilled, experienced labor costs more, and if you introduce non value-added steps like NDT and QA into the process, it drives the cost up. That's just a fact.
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Correct assembly of an AR from decent quality parts is ludicrously easy. Armorers are no longer arcane figures, spoken of with awe and reverence. Mechanically inclined 16 year olds build solid ARs by watching Brownell's videos.
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Correct assembly of an AR from decent quality parts is ludicrously easy. Armorers are no longer arcane figures, spoken of with awe and reverence. Mechanically inclined 16 year olds build solid ARs by watching Brownell's videos.
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So then how do guns get out in the wild with sub-standard staking, etc?
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So then how do guns get out in the wild with sub-standard staking, etc?
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Because more often than not the name on side of the rifle has inherently more value to it that others.
So then how do guns get out in the wild with sub-standard staking, etc?
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In my example, the teenage assembler is buying a complete BCG. I've returned Colt BCGs for poor staking.
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So then how do guns get out in the wild with sub-standard staking, etc?
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Attention to detail and lack of qa/qc.
I'd say it's simple. It's easy for someone building one. Get a bunch of people assembling multiple rifles day after day, it's still "simple", but controlling the process is not easy.
When one guy does something out of spec, but thinks it's good enough, how it it captured and resolved? Or does it ship out? Is that decision made by the assembler on the shop floor?
In my example, the teenage assembler is buying a complete BCG. I've returned Colt BCGs for poor staking.
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In my example, the one you quoted, I was talking about the complete assembly. Some companies are more consistent than others. They just are. Now, I'll give you, some names pop up more than others due to volume of product as well. I'd be interested to know the part rejection % of the various manufacturers.
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Attention to detail and lack of qa/qc.
I'd say it's simple. It's easy for someone building one. Get a bunch of people assembling multiple rifles day after day, it's still "simple", but controlling the process is not easy.
When one guy does something out of spec, but thinks it's good enough, how it it captured and resolved? Or does it ship out? Is that decision made by the assembler on the shop floor?
Exactly this. Lean manufacturing being what it is, QA is more and more going by the wayside. If your processes are not locked down, that can be a baaaaad deal. It is far easier to ensure quality, the lower ones volume, like you said.
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Exactly this. Lean manufacturing being what it is, QA is more and more going by the wayside. If your processes are not locked down, that can be a baaaaad deal. It is far easier to ensure quality, the lower ones volume, like you said.
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OR, you could really save some dough and let the customer do the final testing...[emoji3]
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OR, you could really save some dough and let the customer do the final testing...[emoji3]
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If only everybody thought of it that way....lol
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noonesshowmonkey
01-14-17, 13:08
So, the Battlefield Vegas discussion has produced some really interesting results.
In particular, this gem (https://www.m4carbine.net/showthread.php?192329-Shooting-Range-in-Vegas-sharing-info-on-what-works-and-what-doesn-t&p=2439429#post2439429) that 26 Inf came across.
This specifically addresses PSA BCGs and FN double chrome lined barrels: probably the two strongest arguments FOR what I've been discussing here. That if parts are in spec and made with the right kinds of materials, you get good parts. Period.
Sacred cows under the sword.
So, the Battlefield Vegas discussion has produced some really interesting results.
In particular, this gem (https://www.m4carbine.net/showthread.php?192329-Shooting-Range-in-Vegas-sharing-info-on-what-works-and-what-doesn-t&p=2439429#post2439429) that 26 Inf came across.
This specifically addresses PSA BCGs and FN double chrome lined barrels: probably the two strongest arguments FOR what I've been discussing here. That if parts are in spec and made with the right kinds of materials, you get good parts. Period.
Sacred cows under the sword.
Not quite. The same data shows the Colt bolts being flawless, and so close within spec that the ejector spring failed in 4 different rifles at nearly the exact time/roundcount....
From the excerpt...
Testimonial on Colt:
Quite a few of you have asked about how the Colt M4's are holding up since being put on the line (according to our records, this particular rifle went on the line 02 OCT 15). They have handled very well with no broken bolts, no broken hammer/trigger pins, no eroded gas tubes or any other failures up until this week. I do want to put it out there that the RSO's really like these weapons. They were all outfitted with the exact same Magpul furniture in two different colors to help in swapping out weekly. They all have MOE handguards with a forward pistol grip to help control heat issues. These weapons get hot after several magazines and when you have parties of anywhere from 2-20 people shooting, the weapons are intolerable for the person who's never handled a firearm to enjoy the experience.
That being said, the RSO's have used these weapons every day of the week and migrate towards the Colt's. They have been on the line since the first week of October and as stated above, they haven't suffered from any issues up until this point. The only reason that I am bringing this up is because I was in the armory yesterday morning and I noticed on of the Colt's disassembled on the bench. It was a FDE model and I knew that those models were on the line and shouldn't be down for cleaning. I asked my armorer Danny Boy what the issue was and he said that the ejector spring was in about 7-8 pieces and that it actually happened to be the second one of the morning. I thought that was pretty odd for two ejector springs to go out in the same day. My other armorer Sean stated that he had already replaced two others early this week for a total of four Colt M4's to suffer ejector spring failure in one week. Also, the ejector pin spring sheared upon failure and had to be punched out.
For this rifle to have four HARD months of use and only suffer from a ejector spring failure is really good in my opinion but the fact that four went down with the exact same issue is what's strange. Also, we never saw the usual slow down during the November through February season and these weapons have continued to see high round counts. Without looking at numbers of rounds consumed for the time period it's fair to see these rifles have no less than 25,000-30,000 rounds through them.
Today is my day off but I will send a message to the armorers to go ahead replace all the ejector springs in the Colt M4's as preventive maintenance and to avoid malfunctions with customers on the range.
Thanks for the update. 25,000-30,000 is a lot of rounds for a ejector spring. I believe they have a maintenance plan of 10,000 rounds. So you tripled their expected life.
So given the colts in fact performed better, and at a similar cost to a consumer, you can see why people recommend the 6920 over all other rack grade budget rifles. For the same or a bit more $$$, you get a better rifle.
One difference would be if Company A has all the original drawings for the M4 and makes their AR15s to the drawings and Company B has some drawings for the M4, some drawings for the M16A1 and some reverse engineered drawings and makes their AR15s to that. Then there is the possibility that Company B is also modifying tolerances and materials to their liking.
I assembled an upper receiver group for a buddy with an Aero upper and Daniel Defense barrel. The feed ramps didn't line up and I had to remove material from the barrel extension so there wasn't a lip for a bullet to get caught on. One or the other or both were out of spec. If the upper and barrel were made to the M4 drawings this wouldn't have happened.
So, the Battlefield Vegas discussion has produced some really interesting results.
In particular, this gem (https://www.m4carbine.net/showthread.php?192329-Shooting-Range-in-Vegas-sharing-info-on-what-works-and-what-doesn-t&p=2439429#post2439429) that 26 Inf came across.
This specifically addresses PSA BCGs and FN double chrome lined barrels: probably the two strongest arguments FOR what I've been discussing here. That if parts are in spec and made with the right kinds of materials, you get good parts. Period.
Sacred cows under the sword.
Now wait a minute boys! (Monkey and 188) I posted that info because someone asked about PSA.
What I took from all on Henderson Defense's posts is get out and shoot. An inexpensive gun runs fine for them, more expensive weapons run a little better, but they all run.
Each person should make a decision based on their own needs.
So, the Battlefield Vegas discussion has produced some really interesting results.
In particular, this gem (https://www.m4carbine.net/showthread.php?192329-Shooting-Range-in-Vegas-sharing-info-on-what-works-and-what-doesn-t&p=2439429#post2439429) that 26 Inf came across.
This specifically addresses PSA BCGs and FN double chrome lined barrels: probably the two strongest arguments FOR what I've been discussing here. That if parts are in spec and made with the right kinds of materials, you get good parts. Period.
Sacred cows under the sword.
What does this even mean? Who said that correct parts aren't good parts?
Edit, fwiw, the material is part of the spec.
noonesshowmonkey
01-15-17, 01:02
What I took from all on Henderson Defense's posts is get out and shoot. An inexpensive gun runs fine for them, more expensive weapons run a little better, but they all run.
Which has been the underlying thesis statement of this thread.
There are how many pages of "Is Aero Precision GTG?" and how many PSA threads and how many Spikes and how many [not Colt / BCM / DD / Noveske / KAC / LMT] threads on here?
The idea is simple. We know what the AR-15 is. There is a spec sheet. Colt has the TDP, yadda yadda. But the specifications are known. Given the current state of machining and materials science, the consistency and quality of current manufacture is orders of magnitude beyond what the original design called for.
I am not arguing for PSA or whomever or against Colt or whomever. I don't have a dog in this fight. My fight is with brand loyalty, emotional attachment, hoodoo voodoo street magic, gun-range enthusiasm, etc. over raw data. Henderson Defense gives us data.
I am stating that from a mathematically justifiable, scientifically based approach, the current state of manufacture exceeds the limits on the specifications, leading to extremely high levels of producability for these parts, which were designed for mass production and to be interchangeable.
Henderson Defense's experiences verify this. Which is to say another way, 'get out and shoot.' I'm hardly in the minority on this. There's been plenty of discussion on this topic on other sites, and is a common theme in several MrGunsnGear pieces, just to name a few places where this has come up.
GI drawings have been bootlegged and posted across the interwebs. Any good shop can find the dimensions and materials standards posted, and the .mil inspection and acceptance specs are public domain.
What people can actually buy varies wildly. Caveat emptor.
http://img.photobucket.com/albums/v394/giffmann1/LowerBluePrint1.jpg
http://i1286.photobucket.com/albums/a601/AVIDavid1982/M231KeyandBoltCarrierAssembley_zpsab81ae5f.png
http://i1286.photobucket.com/albums/a601/AVIDavid1982/Extractor_zpsf84b1ea7.pnghttp://i1286.photobucket.com/albums/a601/AVIDavid1982/BoltAssembly_zps12d7bd17.png
GI drawings have been bootlegged and posted across the interwebs. Any good shop can find the dimensions and materials standards posted, and the .mil inspection and acceptance specs are public domain.
What people can actually buy varies wildly. Caveat emptor.
http://img.photobucket.com/albums/v394/giffmann1/LowerBluePrint1.jpg
http://i1286.photobucket.com/albums/a601/AVIDavid1982/M231KeyandBoltCarrierAssembley_zpsab81ae5f.png
http://i1286.photobucket.com/albums/a601/AVIDavid1982/Extractor_zpsf84b1ea7.pnghttp://i1286.photobucket.com/albums/a601/AVIDavid1982/BoltAssembly_zps12d7bd17.png
There are a lot of drawings that weren't leaked though.
My opinion is unqualified and based on study and not experience. In addition to 100% adherence to TDP dimensions, there are so many other physical criteria noted in this thread. And then there is quality control, which is expensive indeed. To give an example of this statement I'll draw on an experience that occurred in 1983. From the Olin Corporation I bought a high grade Winchester 20 gauge double barrel with ejectors. Out of the box one ejector failed. I took the shotgun to a respected repair person suggested by Winchester. I drove to Houston for this purpose. The man shipped it back to me and said he could not fix the problem. The next day I got a phone call from Olin. The man was director of their customer service. He said send the shotgun back. When I receive it, I'll send you another one. During the conversation, I asked what he would do with my gun. He said that it would be studied and then cut in three parts with a welding torch. During this time Olin sold a new product for them--double rifles in various center fire calibers. They were flukes and recalled with the purchaser reimbursed. I discussed this event with the nice man from Olin, and he told me that all these double rifles--good and bad--would be destroyed.
The above example is a level of QC that most companies can not or would not adhere to. Back to ARs. When we venture into areas away from the known, quality control may be a crap shoot. I'm in the dirt clod shooter category but still wish to buy good stuff. Right now I'm working on selling my Expanse upper/Smith lower hybrid to get the real thing even though I probably could continue to get by with the Expanse carbine, which by the way works OK.
The AR is designed to to eliminate "tolerance stacking". It's designed so that when everything is made within tolerance, the parts will fit. If the parts of an AR don't fit or work together, something is out of tolerance
This being the key....
There will be no problem with bin parts if those parts are made to spec. The AR really is a marvel of modern engineering and was far ahead of its time when it was developed. It's the first design to control headspacing to the point all bolts are a drop in fit with all barrel assemblies, a leap forward in rifle manufacturing. It's the first issue rifle to fully embrace modern production methods and it was readily adaptable to manufacturing control methods yet to be developed. That's it's real edge over the M14, AK, FAL and other designs
Well, no.
MG-15s, MG-34s, MG-42s, M61, M60 and M1941 all predate the AR and all have barrel assemblies and bolts made so that any in-spec barrel and any in-spec bolt should headspce together, there are others as well. Anything with a permanent barrel extension with the locking lugs is capable of having this feature, and a few designs without can too, the ZB 30 is such an example.
With the M14 (as originally made, new stuff varies from maker to maker), any new barrel, installed on any new receiver should accept any new bolt and headspace and time correctly. This was done through tight tolerances on the bolt, chamber and where the threads in the receiver and barrel start.
The Johnson idea of barrel extension (designed around 1936) used on the AR makes is very easy and cheap to make such compatibility, but is by no means the first to do this.
GI drawings have been bootlegged and posted across the interwebs. Any good shop can find the dimensions and materials standards posted, and the .mil inspection and acceptance specs are public domain.
http://i1286.photobucket.com/albums/a601/AVIDavid1982/M231KeyandBoltCarrierAssembley_zpsab81ae5f.png
That's an M231 bolt carrier, good luck getting that to work in your AR....
Now wait a minute boys! (Monkey and 188) I posted that info because someone asked about PSA.
What I took from all on Henderson Defense's posts is get out and shoot. An inexpensive gun runs fine for them, more expensive weapons run a little better, but they all run.
Each person should make a decision based on their own needs.
100% agree. I think sometimes, folks forgetting or having never taken the time to acquaint themselves with the nature of the forum, they believe the a/b/c brand argument is "fanboyism". It isn't. There is a very specific "mission statement", if you will.
As you stated, one has to decide if a given rifle is suitable to ones needs. For the small (to me) difference in price between a 6920 and most cheaper rifles, I feel it's a no-brainer. That doesn't mean a cheaper rifle isn't suitable for someone else's purpose.
Regarding sacred cows being slain...I think the results themselves proved that incorrect.
Oh, and I only quoted your post originally because that's where the stats were. [emoji846]
Sent from my iPhone using Tapatalk
I hope you understood I posted that in good humor!
But, yeah, if I was arming a team, it would be with Colt's, otherwise I like to roll my own.
I hope you understood I posted that in good humor!
But, yeah, if I was arming a team, it would be with Colt's, otherwise I like to roll my own.
Lol...yessir. I was trackin [emoji846]
Sent from my iPhone using Tapatalk
That's an M231 bolt carrier, good luck getting that to work in your AR....
Dang, you're right.
Help yourself to these (pages 17 and 18): http://docslide.us/documents/ar-15-m16-blueprint-33-pages.html
Doesn't make a part GI.
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