I remember reading a really detailed post of the issues a year or so ago, but looking through the forum now it appears they scrubbed it. Only thing left is people discussing that post in other topics.

That is true, but it was scaled down with the .222 in mind, not the .223. The military wanted an even hotter round, and the .223 was as far as Stoner would go in terms of pressure.

With all the propietary setups in the market, it amazes me that so few companies address the bolt. Radiused lugs. New extension. Boom. Done.

Actually, they copied it from Melvin Johnson . . .


A Johnson M-1941 bolt, with extractor removed.

EDIT:

Oh, and there fatigue problem long before the carbine variants.  We know this for two reasons:

1) the chrome plated bolts were dropped, due to cracking (guess why), and
2) they specified shot-peening the lugs, the only reason you bother to shot-peen is to reduce fatigue issues.

So because he also used a bolt with multiple locking lugs (looks like the Johnson has more, btw) he "copied" the bolt from him?  Aside from the bolt face, I doubt the rest of of the bolt carrier group design is very similar.  I mean, how many semi automatic rifles are based around bolts with two locking lugs?  At least dozens that I can think off off the top of my head (garand, m14, m1 carbine, Sig 550, Mini-14, AK47, SKS, M249, etc).  Do you complain about whomever you think they "copied"?  Lots of firearms have triggers, but no company tries to claim that the trigger was their invention.  

Also, keep in mind, sometimes minds think alike, and similar designs are conceptualized and created independently with no knowledge of the other.  Just because one person technically thought ot something first chronologically, doesn't mean he was the only one who could have, or did, think of a certain concept.

Pretty sure Stoner invented the operating system, not the bolt lug design. Like you said the bolt design is not an issue. There are also other guns that use the same lug design as the AR. Actually most 5.56 rifles do it seems.

Also the 1941 has room for 9 lugs. Guess Beretta coppied it for their ARX.


Yep AR-15 through and through.

Like this: "All bolts will be replaced at 5,000 round intervals, unless flaws are noted in routine inspections prior to that point.  Round count may be estimated based on unit-level firing schedules per the following table...."  Or something like that.

A bolt is a $40 item for us civilians, and probably costs Uncle Sam $25 at most.  OVER-DESIGNING such a part is not an efficient use of materials or design time, and leads to unnecessarily complex standards - and the accompanying inspection criteria and protocols. Inspect the bolt when you clean the rifle, and if it looks like there are flaws, replace it.

[orange]Well, Kalashnikov basically stated that the AK's bolt is basically an M1 Garand, and they are, along with the trigger mechanism.  And, the M14 and Mini-14 bolts are copies of the M1 bolt.  The SKS uses a tiling bolt.  Once your patent is up, you can copy all you want.  That's why there are patents, so after a time you can copy, because theoretically stuff that works best should be used.

From Stevens' and Ezell's comprehensive tome on the subject:


The lug design is the issue in lug fatigue and failure.

Well, let's be honest, most 5.56mm rifles copy either the AR-15 or the AR-18, to some degree.  And why not?  The tooling to cut the locking lugs in the extension and on the bolt already existed so one supplier could provide spare parts for their own design, or the ever present US supplied product.

Historically in the last fifteen years or so, the Army bought has bolts at around $50 a pop.  (The day of the twenty dollar bolt was in the 1980s)

On 2009/02/04, a 5 year Indefinite Delivery, Indefinite Quantity, contract for $ 35,866,600 was awarded.  The minimum guaranteed order was 20,000 bolts.

So, if the minimum was all the Army needed, they cost - $ 1800 a piece, if the Army (Navy, USMC and AF) bought a million bolts, they were $35 each.  This contract should be ending about now.  I will have to do a little internet digging and see just how many have been delivered under this contract. (Gov't contacts are public knowledge, but they never just publish it.)  We'll see if they need to buy some more.

Designing a part, like a bolt, should be done so it lasts as long enough that we, the tax-payers, don't have to spent 36 million every five years for bolts.

The most recent one was $21,000,000 for 350,000 bolts, I believe. Colt and FN split it from what I read.

My offering was pretty much a "toss it out there" idea.  I'm surprised that the actual cost is about $60 each in that contract - though I don't know how much else is included (spares, etc.).  But it's still not an expensive part even on a gun that might cost $600 delivered.  Like the barrel, the bolt is replaceable, and is considered a part that can (and does) wear out.  So why spend $10,000,000 designing one that wears out 10% later?  Especially when such redesign effort would obsolete tons (literally) of on-hand spares, along with all the installed barrels in the DoD inventory...

Maybe for a new weapon, basing a new mass produced bolt on somewhat more robust designs with far fewer features that look too square, etc. would be a workable idea.  Retrofitting every single AR-type weapon in DoD is not workable in any sense of the word.

The contract is just for complete spare bolts (bolt, extractor and ejector and associated pins and springs) and the packing and shipping of said complete bolts to a place designated by the Army.

Retro-fitting is never a cheap option and usually reserved to safety issues.

The problem as I see it is a typical one for contractor developed projects: it wasn't done right in the beginning.  In the trials they saw the chrome plated bolt was failing prematurely, instead of fixing the design when the cost would have been the smallest*, they put a band-aid over the problem.  Now, years later, it is cost prohibitive to fix it right.

I don't know about you but I think $36 million dollars could be useful elsewhere in the DOD, not for bolts that should last more than 5000 rounds.
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* The big cost in redesigning an in-service part for the military is the paperwork.  During development, the governments hand isn't quite as deep, so the paperwork cost is less.  The problem is the contractor usually has to do more work and allocate more manpower to fix the problem (depending on how the contract is written, they may have to bear the cost as well), so usually their management wants the fastest solution that will alleviate the problem.  Once it sells, the government bears the cost of maintaining it, so if the solution is not the best, meh, they aren't as worried.  They do care, just not enough to spend shareholder money on it.  Sometimes they do, if the problem turns out to be big and embarrassing.