Case mouth bulge or bell on sizing .260 Lapua

[TimK]

Rem .260
Lapua Brass - 6 cycles
Redding S full length bushing sizer, .293" bushing with the expander ball
Loaded neck diameter = 0.294"

I'm getting a condition where the last 0.050" of the case is bulged or belled about 0.004" The main diameter of the neck measures 0.293" after sizing, and the very end of the mouth measures 0.297" The bulge starts about 0.050" from the mouth. I don't remember seeing this when the brass was new, but I may not have been looking. It got so bad one loading that the rounds wouldn't chamber. I didn't think to measure those. I'm also getting some shaving of the bullet when seating, even with a light inside chamfer from a standard (not VLD) deburring tool.

My chamber dimension is 0.299" (fired brass measures 0.298"), and there is no lip or bulge present on fired brass. It's clearly a product of the sizing process.

Thinking the brass might be getting hard, I annealed 25 pieces this morning. They showed the same bulge after sizing. I have not seated bullets yet so I don't know if it will still be shaving copper.

Any idea what's going on? Is this just normal and I've never noticed?

 

[Beef Curtain]

Is your bushing tight down in the die?
Bushing installed numbers down?

 

[Bluejazz]

Are you using the depriming stem with the bushing? The depth might not be set correctly

 

[Beef Curtain]

Are you using the depriming stem with the bushing? The depth might not be set correctly

This may also be the case. The expander ball and/or the de-priming stem may be bottoming out inside the case and not allowing the case to be fully seated up in the die.

 

[TimK]

Bushing not tight, numbers up. Deprime stem is installed but not contacting the case. Cases are deprimed and cleaned before sizing.

 

[Beef Curtain]

It goes in with the bushing number size facing down (it has a .0005" taper), and give it about 1/8 of a turn of slop to let it float and thereby center on the case neck.

 

[milo 2.0]

What you are experiencing is the dreaded donut, it's on the inside of your case also. I'm going through the same shit. Your brass is allowed to expand too much in the neck, the bushing die doesn't take it all the way to the shoulder, soon no cases will chamber.
You need to neck turn, plain and simple.
I startd a thread last week on it here, maybe page 3. I will post tonight on my findings in what I bought.
Here's two links:
https://www.kmshooting.com/

21st Century Shooting

Unless your case mouths are dinged, loose the expander ball, it serves no purpose.

 

[TimK]

It goes in with the bushing number size facing down (it has a .0005" taper), and give it about 1/8 of a turn of slop to let it float and thereby center on the case neck.

I'd have sworn I remembered reading the numbers went up. I just looked on Redding's site, and they say down like you though they don't mention the taper. I measured 4 different bushings and couldn't detect any difference in diameter, but I was using a cailper.

I don't think I have any more unsized brass to try at the moment.

 

[TimK]

What you are experiencing is the dreaded donut, it's on the inside of your case also. I'm going through the same shit. Your brass is allowed to expand too much in the neck, the bushing die doesn't take it all the way to the shoulder, soon no cases will chamber.
You need to neck turn, plain and simple.
I startd a thread last week on it here, maybe page 3. I will post tonight on my findings in what I bought.
Here's two links:
https://www.kmshooting.com/

21st Century Shooting
Unless your case mouths are dinged, loose the expander ball, it serves no purpose.

I was under the impression that the donut occurred at the base of the neck, not the mouth. Am I wrong? Also, I looked back 3 pages and couldn't find your thread. Got a link?

 

[Beef Curtain]

I'd have sworn I remembered reading the numbers went up. I just looked on Redding's site, and they say down like you though they don't mention the taper. I measured 4 different bushings and couldn't detect any difference in diameter, but I was using a cailper.

I don't think I have any more unsized brass to try at the moment.

When I spoke to Patrick with Redding at SHOT. That is what he told me....

 

[milo 2.0]

I was under the impression that the donut occurred at the base of the neck, not the mouth. Am I wrong? Also, I looked back 3 pages and couldn't find your thread. Got a link?

Wow, I guess I didn't read it right, donut is at the base of the neck, sorry. I don't have a clue what you have going on, usually this happens to me first!
Post some pics if you can.

 

[TimK]

Here's a pic.

The larger diameter starts only 0.050" or so from the mouth.

 

[TimK]

When I spoke to Patrick with Redding at SHOT. That is what he told me....

I believe you, but it surprises me I couldn't see a half thou with a caliper. I'll flip the bushing next time and see if that helps.

 

[arnie19]

What your seeing at the bottom of the neck is normal when the bushing isnt long enough to size the neck all the way down the neck .I personally like to keep that larger area so it helps align the case neck centered when closing the bolt . If you want to get rid of it you need to shove the case farther into the die but that cant happen unless you shave some material off the bottom of the die .Arnie

 

[TimK]

What your seeing at the bottom of the neck is normal when the bushing isnt long enough to size the neck all the way down the neck .I personally like to keep that larger area so it helps align the case neck centered when closing the bolt . If you want to get rid of it you need to shove the case farther into the die but that cant happen unless you shave some material off the bottom of the die .Arnie

Again, the bulge is at the mouth, not the base of the neck.

 

[Bluejazz]

It seems to me that the button on the depriming stem is existing the neck area before the bushing sizes the neck. Just a guess. Try setting your depriming stem deeper so that it is pulled thru the neck while the bushing is sizing the neck

 

[oldfatguy]

Big change in methods but you might try a Lee collet neck sizer.

OFG