Shoulder collapse

[Germz]

I was loading 300 blackout yesterday and I was making a dummy round. When seating the bullet with my hornady die the shoulder collapsed in on itself. I figured it was just a fluke but it happened again.

I'm not using anymore force than I normally do with any other caliber. What is causing this?

[bsumoba]

was this factory new brass or "made" from 5.56/.223 brass?

could be improperly sized case shoulder/neck or too soft of a neck/shoulder (over annealed?)

[Germz]

made. LC brass.
I think its because the case mouth is getting caught on the powder coating of the bullet. I deburr the case mouth pretty well...so I'm not sure.

[russt]

Too much crimp, crimping too soon is what it sounds like. Back the die out raise the ram to the top with a case in it, screw die in until it touches case mouth then back it off 1/4 turn, now place bullet in case and adjust seater plug until bullet seated to proper depth. Then your done unless you want to crimp, if crimp is desired back seater plug out about 3 turns, then screw die down 1/4 turn and run the case up again, keep repeating until proper crimp is achieved. Once crimp is good run finished case to the top and screw seater plug in until it touches bullet.

[LynnJr]

The bullet pushed on the neck enough to collapse the shoulder.

Causes can be too much neck tension caused from thicker brass or brass sized down too much.
Not enough chamfer on the neck or leaving a burr.
Flat base bullets especially custom bullets are finicky with thin necked cases.
On my 300 Whisper I use a 22 degree carbide burr to chamfer the already very thin 221 Fireball brass and still get an occasional collapse and I don't crimp any round ever.

[74c5]

Double check the die installation and lock down for height and offset from the shell holder. Usually 1 turn out before setting the bullet location.

[bsumoba]

made. LC brass.
I think its because the case mouth is getting caught on the powder coating of the bullet. I deburr the case mouth pretty well...so I'm not sure.

if there is a powder coating on the bullet, then you probably have too small of a neck size. you might need to file down your expander ball. Measure your bullet diameter thickness and compare to the ID of your neck.

[Fjold]

Too much crimp, crimping too soon is what it sounds like. Back the die out raise the ram to the top with a case in it, screw die in until it touches case mouth then back it off 1/4 turn, now place bullet in case and adjust seater plug until bullet seated to proper depth. Then your done unless you want to crimp, if crimp is desired back seater plug out about 3 turns, then screw die down 1/4 turn and run the case up again, keep repeating until proper crimp is achieved. Once crimp is good run finished case to the top and screw seater plug in until it touches bullet.

This is probably correct. It's one of the most common errors in setting up new dies.

[Flyin Brian]

if there is a powder coating on the bullet, then you probably have too small of a neck size. you might need to file down your expander ball. Measure your bullet diameter thickness and compare to the ID of your neck.

Filing down the expander is not going to improve the situation.

[knucklehead0202]

Filing down the expander is not going to improve the situation.

exactly what I was thinking as soon as I read it.

[bigred1]

Too much crimp, crimping too soon is what it sounds like. Back the die out raise the ram to the top with a case in it, screw die in until it touches case mouth then back it off 1/4 turn, now place bullet in case and adjust seater plug until bullet seated to proper depth. Then your done unless you want to crimp, if crimp is desired back seater plug out about 3 turns, then screw die down 1/4 turn and run the case up again, keep repeating until proper crimp is achieved. Once crimp is good run finished case to the top and screw seater plug in until it touches bullet.

Bingo! Back your die out a bit.

[Germz]

Hmm, I already had it backed out a full turn from the shell holder...I'll try a little more. Thanks!

[bigred1]

What kind of press are you using? I was having the exact same issue on my Hornady LNL single stage using my RCBS dies. I had to back my seating die off a lot. I'll try and get a measurement for you tomorrow but it was more than 1 turn.

[Bumslie]

Did you measure the ID of the neck? Maybe you have to ream it out?

[Cheep]

You may have to flair the case mouth like a pistol cartridge if you are using lead with powder coat.