I find the NEA Kaboom pretty odd actually, as Dave claimed at the time the barrel extension apparently did not fail although the receivers did fail, and it would appear he hasn’t changed that stance. I am no expert but after some extensive internet research, yeah I know, I have yet to find a 7075 forged receiver fail like this. From what I could find, which was quite a lot, every instance of a 7075 receiver failing was in conjunction with the barrel extension failing.
So I could only conclude that a forged 7075 receiver is strong enough to contain a Kaboom unless the blast is so great the barrel extension fails. Bolts, carriers and mags all destroyed but NOT the receivers. In fact I would say the AR was designed to fail in this exact way, containing the blast and releasing out the mag well, typically peeling the carrier like a banana. I have seen the same peeled carrier as the NEA kaboom, but never with bulged receivers.
So, if someone would like to show me a forged 7075 receiver that has failed, but the barrel extension has remained in tact I would be very interested.
I am of the opinion that forging the receiver is important.
Looks like NEA heard you and has allowed me to release some info. Which I am thankful for because there is a lot of speculation here and opining without anyone having any actual experience in testing this material in this application, while others certainly have. As any engineer will tell you that no material acts the same across the board, in all forms and in all applications. In a Apples to Apples comparison of two separate 'blocks' of aluminum, then yes several assumptions will be able to be made.
As they say, a picture is worth a thousand words. In ALL cases of failure in testing, not a single upper received what we would call a "catastrophic failure"; that is they did not lose structural integrity and break, spall or fracture completely. Incidentally two uppers and two lowers were "hammered back into shape" after their first failure and were test fired successfully. They were again, subjected to another failure test. Why? Just to see if it could be done. If your AR blows in the field can it be put back into service with just a rock and a new BCG? Scientific? No. Fun? Certainly!
Furthermore no barrel or extension suffered catastrophic failure. In fact most of the test barrels were able to be pulled, inspected and reused without any repair. In all tests only one barrel extension received any damage, a hairline crack that was detected at inspection. What these pictures clearly show is that the safety features engineered in the design all worked as they should. The explosive force was directed through the extractor cut, split the carrier, and the force was directed down and away from the shooter. The receivers did not break or crack fully (only one receiver cracked at all). As well, the barrels with one exception were found to be completely undamaged. The procedures and data from these tests can not be released, nor what was done to simulate these conditions but I can share the results and discuss what is seen here.
What the following shows is controlled and repeated results under several conditions.
That is actually the picture Dave first provided when he posted the NEA Kaboom. IIRC the receiver extension did fail, the crack is right at the top where the receiver split. Not sure about the second picture…
I know it is one hell of a statement to make, perhaps why I have not done it sooner, but you have to admit I do have a bit of a point… the 6061 billet receiver is flexing where as a 7075 forged receiver would show no signs of damage in the similar situation.
Yes that picture was posted previously as a comparison of similar force. But your statement about one receiver flexing while another shows no sign of damage is unsubstantiated. Unless you have tested both platforms in identical conditions and can confirm that.
The metal characteristics are interesting academically but ultimately a red herring. 6061 is a lower spec. It's place in the market is for the low end comercial product.
I don't see any point in going with a 6061 lower. Sure it's billet and an excellent price for billet. But so what? A forged 7075 lower is abouT $10 more. If the billet lower offered ambi or something more then I could see it. But let's face it the price difference in the long run is minimum. Unless you're trying to make a super cheap build with the cheapest ok parts you can find. Even then Norinco has that locked up.
So where does the 6061 billet lower fit? Not the cheapest, not middle or high end. Cheap go Norc with 7075 forged. Middle go Aero, Palmetto armory etc with 7075 forged and excellent finish. High end there are 7075 billet and forged with ambi featured and perfect finish.
The decision to go 6061 however was penny wise and pound foolish. Marketing clearly wasn't looked at with this in mind. That as a company was short sighted.
6061 is a "lower spec" lower than "what" spec? 6016 T6 is the most common material for AR accessories and components that are manufacturer in-house. 7075 is most common in receivers because they are provided in that state by the forge and finished in house. 6061 is also used in more high stress applications in the aerospace industry than 7075. And as I just learned by 1965BJS's post above "If a 140mph Marathon jet boat hull can be made of 6061 material, run in 2" of water and last through years of race use, it will work fine as a lower for any firearm!" Neither of those applications would be considered "low end commercial". 6061 is was not chosen because of price certainly. If that was the only consideration not having to defend the change would be easily worth the $10 more in raw material cost. Two deciding factors (but not limited to) were reduced run time vs 7075 and properties that 6061 possesses over 7075. Run time on a million dollar automated CNC center being the single greatest cost in construction. 7075 is chosen for receivers primarily because it forges very well. It has nothing to do with it's strength over 6061, it is purely a result of its specific production properties and requirements (with the addition that in the US military put that number on paper, it is stated by name in the MilStd).
Norinco AR receivers are stated to be 7075. Do you believe it to be the same 7075 that the US forges use? If this is an apples to apples discussion...
Why was 6061-T6 chosen by this manufacturer? Ease of machinability, decades of engineering experience with the material, increased corrosion resistance and a targeted end user. Marketing was a huge decision in its application in fact. There is no other AR made with so much consideration towards corrosion resistance. No one goes into a project of this type without looking to the horizon. Decisions have to be made at the start that will affect what happens in the future. (obviously this is a double edged sword as we've seen too many times
).
Is a billet receiver better than a forged one? No. But it does offer a level of creativity for a manufacturer. Is 6061 as a material better than 7075? Again no. In what application? Each has its merits to specific applications. I would however argue that in this application, there is evidence that a 6061 receiver will absorb a failure better than a 7075 receiver. Why? Again, I can theorize all day but I'm not an engineer. But there are people that have done more than just speculate online and quote Young's Modulus. There have been tests, data gathered, and decisions made based on those decisions. I've been lucky to have been privy to that data. I am also in the unique position to have seen the catastrophic effects of a rifle that has blown and seriously wounded a friend. There are few I would say in that position. With this information and first hand experience I can say that without a doubt that they made the right choice. Was the decision made because they believed that it would better contain a failure? Certainly not, but you'd have to admit that as far as side-effects go it's a bit of a golden egg.
You will have to admit that the pictures above show that the results weren't one-off's, they are repeatable and consistent. These are the the type of results that provide an accurate conclusion. Will a NEA receiver kill you and your hamster in your sleep? Nope.. but as Hungary says, they may make your #### fall off so get two of them.
