grayfox Wrote:I dont think we know the angle in deg, but might be able to measure the diameters at the breakpoints, IOW the inner, chamber diameter should be close to constant but the outer diameter of the innermost radiusing smaller diameter I would infer that its cone is smaller. Larger dia would infer a deeper radius, if the cut angles are all equal. Its 4 am, hope my brain is thinking straight.
edit to add, I dont think it is correct to say lapua brass was weaker as we dont know the alloys nor the yield strengths for any of the brasses, but it can be said that the brass is thinner so could be more susceptible to a hot gas failure. And the gas pressures for a carbine system vs rifle length system, a 12 will have most likely a clgs, pressures at unlock in clgs are higher than in a longer gas system.
Even if we just knew the radial thickness, as a first approximation we could assume the angle is 45 deg which would make the depth the same value due to the trigonometry. A right angle triangle with the other sides at 45 deg angles will have the same lengths. This would give us a ballpark size.
By weaker brass I meant it to be all encompassing until we have more data. This is exactly why I said just weaker 'brass' as opposed to saying weaker 'Lapua brass'. I wrote it that way for a reason...need more data. As I stated it could simply be a few defective cases. OP stated other brass had the belt phenomena.
And I completely agree it could have been heat! I posted this theory earlier. OP said it was round #41 of 50. OP said the belt phenomena happened to at least one other case before the failure. We all know a barrel gets hotter during a shooting session. To me heat is most definitely on the table! And it is also encompassed in my general statement of 'weaker brass'. Added heat will weaken the metal initially by making it softer, assuming it's not hot enough to change the molecular structure of the metal.
And I absolutely would LOVE to see all the metallurgical and materials science data between Lapua and other brass! I mentioned this earlier too. I want to see the Young's modulus, shear modulus, tensile strength, hardness, and various other factors on all manufacturer's brass! They would give me a much clearer idea as to which brass, all other things equal, is stronger and weaker. Until then we can only speculate, which is why weak brass is still on the table.
And please note that *if* we do find that they all have the same materials science factors, then for sure the less brass at the head for Lapua makes it inherently weaker at that point.