Seating Depth - Thinking Outside the Box

[gunsandgunsmithing]

Where I have seen it happen is when a wildcat gains enough popularity to be commercially produced and the original cartridge has become obsolete. Have seen it a couple times.
Where I specifically ran into a problem was using 280 Remington brass for 270 Winchester. The neck is shorter on the 280 so necking down to 270 was a problem. Technically this would be reforming more than simply necking down, but it gave a memorable lesson.

Yeah, my point to ELR was just that necking up requires part of the shoulder become the lower part of the neck. But I agree with you too. There are examples like yours too, that create similar issues. I guess I was just speaking generally, ie necking up a 6br to 30br. Necking down actually makes the shoulder longer.. fwiw. I neck down a lot of 6.5 Grendel brass to 6 and 22 cal. Using a redding bushing die, the shoulder gets long enough that the die bushing can size all of the neck after necking down from 6.5 vs only most of it. If I neck up to 30(30 Major), the bushing can not size all the way down the neck. Same brass, same die. Hope that makes sense. But it does happen.

 

[dellet]

Yeah, my point to ELR was just that necking up requires part of the shoulder become the lower part of the neck. But I agree with you too. There are examples like yours too, that create similar issues. I guess I was just speaking generally, ie necking up a 6br to 30br. Necking down actually makes the shoulder longer.. fwiw. I neck down a lot of 6.5 Grendel brass to 6 and 22 cal. Using a redding bushing die, the shoulder gets long enough that the die bushing can size all of the neck after necking down from 6.5 vs only most of it. If I neck up to 30(30 Major), the bushing can not size all the way down the neck. Same brass, same die. Hope that makes sense. But it does happen.

My only point is with handloading, absolutes will sooner or later bite you in the ass. There are a lot of posts that seem to almost draw a line in the sand and use the dreaded “always” and “never” words. My interests and therefore experiences generally lean towards cartridges that are not mainstream. I’m not a high end benchrest long or short shooter. But the knowledge, tools and techniques used to get that type of winning accuracy, have gotten many rifles off the walls, out of safes and back on the range than I can count. Wildcatting and that knowledge base combined with the BR knowledge makes a lot of things possible.

Makes these discussion very worthwhile to hear from some very knowledgeable problem solvers.

 

[Doom]

Clearly, you’re an idiot.

Forward upon firing. Rearward upon sizing. There’s no arguing that.

Ignorance is bliss though, so enjoy it.

Maybe. I went back and I took your description "neck/shoulder junction" and "accordion" as meaning the neck/shoulder junction moved back and forth and didn't change material. .

On firing the case body expands and grows to fill the camber space (length and diameter). The shoulder may or may not be reformed but the case overall length will actually decrease slightly depending on the chamber diameter datum length and actual headspace dimension. The shoulder does not move rearward on resizing, When the case enters the die the body diameter is decreased pushing the existing shoulder further up into the die. As the case continues into the die the existing shoulder (which is longer than the required datum length of the shoulder) encounters the shoulder portion of the die and is reformed from a portion of the body and the existing shoulder. The neck is then reformed from a portion of the shoulder and the existing neck. The donut is the result of the shoulder material migrating to the neck.

 

[JFrank]

I’m not sure how the thread went from seating depth to case sizing , shoulder bumping and calling someone an idiot which is completely unnecessary ( BTW) but my cases grow both radially and length when fired and I don’t get doughnuts. Regarding seating I’m with Tom.