On aluminum cases burn-through issues


#1

The thread titled “6x45 SAW phenolic varnish on case?” mentions an earlier thread, author unknown, in which the following post can be read:

As I understand it, the 6x50 length was developed for the aluminium case, because to avoid the risk of “burn through” (aluminium being potentially inflammable) the case interior was lined with a fireproof material. This reduced the case capacity so the case was lengthened to compensate, in order to match the ballistics of the 6x45.

There are a couple of reports of interest in case someone wants to dig deeper into the aluminum case burning issues:

AD-750 379
AN ANALYSIS OF 5.56MM ALUMINUM CARTRIDGE CASE BURN-THROUGH PHENOMENON
Walter H. Squire, et al
Frankford Arsenal, Philadelphia, Pennsylvania, 1972

dtic.mil/cgi-bin/GetTRDoc?AD … tTRDoc.pdf

Technical Report ARAEW-TR-05003
ALUMINUM CARTRIDGE CASE CONCEPT
Armament Research, Development and Engineering Center, Armaments Engineering and Technology Center (Benet)
Picatinny, New Jersey, 2005

I found this last one in the Internet too but now I can’t seem to remember where.

Cheers,

Schneider.


#2

Thank you Schneider!


#3

The second report can be found here:

http://handle.dtic.mil/100.2/ADA434633


#4

Projects to develop aluminium alloy small-arms cases get revived every few years because of the huge weight reduction compared with brass. There’s one research project running at the moment in the USA.

Of course, US-developed light-alloy cases have been in service for decades in 30x173 and 30x113B calibres, so it can be done!


#5

On an alloy case project that I was involved in the case had been developed to a reliable standard when the project had to be abandoned. The problem was that the case was fine when fired from a standard sized chamber but when fired in an oversize one problems occurred. As there were many weapons about with oversize chambers the project died for safety reasons.


#6

[quote=“TonyWilliams”]Projects to develop aluminium alloy small-arms cases get revived every few years because of the huge weight reduction compared with brass. There’s one research project running at the moment in the USA.

Of course, US-developed light-alloy cases have been in service for decades in 30x173 and 30x113B calibres, so it can be done![/quote]

Yes, I find it funny that the concept works with large calibers but not with small arms ammo.


#7

It also works with pistol ammo, of course, with the Blazer series (IIRC). Presumably the lower pressures pose fewer problems.


#8

Here’s a dramatic illustration of a burn-through/case failure. The case is an unheadstamped Canadian experimental 20x110 HS from the late 1940’s - early 1950’s.


#9

Paul, thank you for sharing, it almost looks like a piece of art.


#10

Quite graphic, yes.

As Dale M. Davis puts it, a split in an aluminum case is an entirely different matter and is, to say the least, spectacular. The situation is that although hot powder gas may leak through a split in a brass or steel case and slightly melt or erode the split, a similar leak in an aluminum case will ignite the aluminum which, under the pressure and flow velocity involved, will generate enough heat to melt or burn steel chambers and bolts.


#11

Schnieder - exactly the source I consulted! I was only going to add that it is one thing for such a failure in a remotely operated gun and another when it is mere inches from a shooters face.