450b Chamber Design Question

[gunnut]

Hoot, My man! I thought you started this to find out if the brass would shrink to the point of being un useable. Would be nice to know what that is or if they shrink to a point and stop.

[BD1]

I, for one, am still interested in "how short is too short". So, I'm hoping hoot continues down this road a bit.

Hoot, I don't know why you would be getting shorter on one side of your cases more than the other. However, in general if you are seeing any lack of concentricity develop due to the firing/sizing/reloading process, the first place to look is at the alignment of the dies to the press. Reloading presses and dies have manufacturing tolerances like anything else, and at times tolerances can stack in one direction. I once owned a press that had been bored off center enough that you could readily see the case being torqued to one side as it went up into the die. A quick and dirty check is to set the base of the case on the fat leg of a good machinists square and rotate it, watching to see if the case head is square to the long axis of the case all the way around.

Rifle chambers also have tolerances, but in my experience those tolerances are pretty darn tight in modern firearms.

It could also be that the brass is thicker on one side than the other?

BD

[Hoot]

Oh, I'll continue, just not so rabidly.

I've measured a lot after reloading and before firing and as far as I can tell, they're square as possible.

Ponder this.
The chamber isn't real tight against the case walls when seated. Given the mouths don't touch the lip to keep them square. Given they're being held back one one side by the extractor claw and pushed forward on the other side by the ejector plunger. Perhaps they're canted in the chamber ever so slightly and one side grabs the walls a little tighter upon ignition. Perhaps the extractor distorts the rim beneath it slightly stretching it so the case appears longer on that side, but that would not explain the asymmetrical sooting. I should mark the claw side with a sharpie dot when I hand feed them ( 500 shots so far all hand fed) I know that when I see sooting, it's mainly down one side and I know from reading on these forums that other members experience that as well. As for length variation, it runs about .001-.0025 from one side to the other. More pronounced with lighter loads. I just trim them after resizing so the high side is brought down to the low side. It's NBD, just another enigma. It's 08:30 and I'm off to the range. Have a fun Saturday everyone.

Hoot

[Hoot]

At the range Saturday, I marked each case with a sharpie line right at the mag lip. Given the amount the bolt rotates into lock, it appears all the sooting on light loads occurs on the side favoring the ejector, whereas maximum shrinkage occurs on the side favoring the extractor. Ponder that...

Hoot