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Not sure of the niceties and fine points.  While the equipment is Uncle Sam's it is run by the contractor (Government Owned - Contractor Operated, or GOCO).

Uncles Sam pays the contractor for finished product.  If it doesn't pass compliance Uncle Sam doesn't pay -- Sam's not going to be stuck with wasted components assembled into "Stuff" that doesn't meet contractually-agreed drawings and specs.

When Remington ran Lake City they used IMR and Olin powders.  When Olin ran it they used Winchester-Olin powders.  Now that ATK runs it they use ATK and General Dynamics powders.

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It would be appreciated if someone, more learned than me, with IMI lot 212/G ammunition, would checked the powder charge of this lot with older IMI M193 lots.  Also, if a chronograph comparison could be taken between this lot and older lots.

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Uncle Sam DOESN'T take possession of it until it passes inspection.  There are milspecs for acceptance, not necessarily for rejection.

De-militarized perhaps, but I would imagine that's because it didn't pass acceptance batch-testing protocols.  It'll still safely go "Bang," but it may not have met or exceeded acceptance standards.

Uncle ain't paying for stuff that didn't pass.  He ain't paying a contractor to waste his raw materials, either.

ATK, being stuck with new/excess inventory, may not have to sell or de-mil it if it was never accepted (under contract clause).  If it's safe he can just out-right sell it for profit.

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My understanding was somewhat different from what you're saying, but your points make more sense.  However, I will repeat: Federal stated several times that XM ammunition was NOT rejected GI ammunition, but made with the same tooling and to "civilian specifications," (as in not necessarily having primer sealant, case mouth sealant, being as consistent as required by DoD, etc.).

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That's not "required" by civilian standards, but if they use the LC hardware to make those rounds, it may just be simpler to go ahead with those steps.  My XM855 looks just like GI ammo down to the stripper clips and cardboard sleeves.  I would still expect that they skipped most of the extensive testing required by DoD.

They never said XM (any of them) were overruns, but they never said otherwise.  They STRONGLY stated that (since at least 2005, anyway, when they finally addressed this issue) that the XM lines were NOT rejects or "floor sweepings".  Before then there were many reports of XM193 looking very much like floor sweepings, but that apparently improved quite well.

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No idea. It gone

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PSA:  The freebore is part of "the chamber".  Basically speaking, a chamber consists of:

>  the body

>  the shoulder

>  the neck

>  the freebore

>  the leade

So to answer your question, any particualar chamber can have combinations of the above dimensions.  

Also, freebore isn't just a matter of length, it's also a matter of diameter.  For example, the freebore of the 223 Wylde chamber is narrower than the freebore of a 5.56mm NATO chamber, lending to its improved accuracy over a NATO chamber.

Additionally, the angle of the leade can come into play in the various chambers along with all the other variables.5.56mm NATO versus 223 Remington:  Chamber Differences


A SAAMI spec .223 Remington chamber will have a shorter leade with a sharper angle to the leade and a shorter amount of effective freebore than a 5.56mm NATO chamber. The freebore itself will also be narrower in the .223 Remington chamber.

http://www.box.net/shared/static/oobedcsfkc.jpg
raw pics courtesy of Ned Christiansen


With all other things being equal, the 5.56mm NATO chamber with its longer and shallower angled leade and longer amount of effective freebore will produce less chamber pressure than a .223 Remington chamber, when firing .223 Remington SAAMI Spec ammunition. Because of this, 5.56mm NATO amunition can be loaded to a pressure that would be considered excessive in a .223 Remington chamber, yet acceptable in a 5.56mm NATO chamber. (Pressures are measured using different methods between the two systems.)


The leade of a SAAMI 223 Remington chamber.

https://app.box.com/shared/static/uq9opx0xilyiuna58f75xmiqr2lsf04a.jpgThe official SAAMI 223 Remington drawing.

http://www.box.net/shared/static/kohxuqcxcp.jpg



http://www.box.net/shared/static/hcqot2dmni.jpg


From Jeff Hoffman, co-owner of Black Hills Ammunition

“The 5.56 IS a higher pressure/velocity cartridge, but it is made to a military standard, with different test methods, (and therefore is not easily directly comparable to .223 pressures) . . . the general spec for US 5.56 ammo is 58,700 psi max, measured at case mouth. . . Please note this is a different method than SAAMI transducer or copper crusher, as used on commercial ammunition. 5.56 ammunition spec results in ammunition loaded to a higher pressure level than commercial .223, but the test methods specified are different . . .The spec calls for a different pressure test method than SAAMI spec ammo, and is not directly comparable . . . “


Here's a very interesting quote posted by Ned Christiansen on M4carbine.net:


". . . In short, you can safely fire all 5.56 AND 223 ammunition in a gun properly chambered for 5.56. You MUST NOT fire 5.56 ammunition in a 223 rifle. As case in point, I fired XM193 5.56 ammunition in a 223 test barrel with average pressures (conformal transducer) of 72,550 psi, and peak pressure registered at 76,250 psi. . ."  

Since the SAAMI MAP for the .223 Remington is 55,000 PSI, that puts XM193 fired from a minimum spec .223 Remington chamber at 17,550 PSI over the maximum.


(The following is just a generalization to give a graphical demonstration of concept. DO NOT hold me to the exact numbers as they are not correct and they ignore the difference due to the different methods used to measure chamber pressure.)

Consider the left graph pictured below; M193 fired in a 5.56mm chamber. The pressure is within the MAP limit. Now, take the exact same round, (same powder, same charge of powder) and fire it from a .223 Remington chamber; pictured in the right graph below.

Because the .223 Remington chamber has a shorter and sharper angled leade compared to the 5.56mm chamber as well as a shorter effective free-bore, the bullet engages the rifling sooner in the .223 chamber than it would have in a 5.56mm chamber. This causes the pressure to rise faster, peak sooner and reach a higher (and per SAAMI, unsafe) level than it would have if the round had been fired from a 5.56mm chamber.


http://www.box.net/shared/static/rkuh8gzlj2.jpg



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