Got a bulge...

[Gregg C]

But it's not where I thought folks talk about.

When I hear about bulging necks, I had thought it was at the neck/shoulder junction, not the case mouth. I trim every shot, with a 3 angle RCBS trimmer. I anneal every shot. I deburr with a VLD type tool, Lyman. Every shot. In the process of acquiring pin gauges.
33XC cartridge. Peterson brass. Tubb dies, with a neck bushing, currently running a .363 bushing.
Can somebody tell me how this forms, and how to stop it? It can not possibly be helping me !

 

[MagnumManiac]

I would be looking at the chamber…
If not that, then your bushing is not sizing the case mouth.

Cheers.

 

[L.Sherm]

I agree on looking at the chamber, looks to me like you got brass flowing to the end of the neck if this is a fired case.
If it is I would be looking at the reamer as the culprit.

 

[Gregg C]

Hmmm... They come out more square .

 

[rdr59]

You might be putting to much pressure on the trimmer . Push easier on one and see what happens. Thanks

 

[Gregg C]

That is actually a sized case. I'll take a look in the chamber, best I can, anyway.
I'm not sure what it is I should be looking for, though. How would a reamer cut that shape into the metal?

 

[Gregg C]

You might be putting to much pressure on the trimmer . Push easier on one and see what happens. Thanks

This....makes sense. Possibly. I'll give it a try, thanks.

 

[Gregg C]

Too easy, tho!!

 

[RPrice]

I don't see how a reamer could cause that. Trimming sounds more logical.

 

[VinceMule]

A tube micrometer should be used to measure the thickness, And a regular micrometer that measures the .0001 would help you decern dia of the neck change and neck wall thickness.

The bright ring around the end of the case mouth indicates that the end of the case is scraping somewhere.

Magnum's and Sherm's posts are noteworthy. A carbon ring at the end of the chamber may create a slight bulge when the case is chambered, similar to if the brass is just too long, the magnum's post of "look in the chamber" is the first and easiest thing to do. If you blacken the end of the case mouth with a candle or cigarette lighter, chamber the round, if it is touching either carbon or end of the chamber, it will rub the soot off the end of the case mouth.

 

[Mike D Texas]

That is actually a sized case. I'll take a look in the chamber, best I can, anyway.
I'm not sure what it is I should be looking for, though. How would a reamer cut that shape into the metal?

Your bushing is doing that.
What brand bushing are you using?

 

[Seabeeken]

Ive seen it before. What is the neck diameter of a fired case and a sized case? Seen this before. not a reamer issue.
Mike is correct. IME the neck rises above the bushing while the lower neck is being sized and brass flows forward and expands the unsupported rim of the neck.
I should add, it happens in standard FL dies also when end of neck rises above the neck sizing area of the die

 

[MagnumManiac]

I will elaborate on my post, if just the bushing is being used, no expander, then it is your bushing.

Cheers.

 

[L.Sherm]

I don't see how a reamer could cause that. Trimming sounds more logical.

If its not ground properly!!
The very end of the neck is bigger than the rest.
Most saami reamers are ground with some taper in the neck.