Anyone else having issues with .284 win brass in a K31?

[Loki610]

After I got my K31 I found a 100 good new brass in .284 win before I found the proper 7.5x55 on Tradex.

After sizing I lost about 10% due to split necks. Trimmed and sized using the Lee dies about half of them wouldn't quite chamber without the bolt having to be roughly palmed closed. I adjusted the die and still had the same issue.
Next step I fireformed them using a 150 grain .308 cast and powder coated bullet with 10 grains of unique.
Accuracy was surprisingly good with 2" groups at 100 yards 6" to the right of point of aim with sights set for 400 yards.

The next sizing once again more than half of them didn't want to chamber hanging up on the case web where it seems to be oversize. I tried screwing the die down farther and it didn't seem to make any difference. I'm now on my third loads with this brass and still with the same issues. Accuracy has been outstanding and I'm not seeing any pressure signs nor am I close to max loads.
Once it's empty this time its going in the trash.

Just curious if anyone else has been using .284 win brass and having the same issues.

 

[samsplacci71]

After I got my K31 I found a 100 good new brass in .284 win before I found the proper 7.5x55 on Tradex.

After sizing I lost about 10% due to split necks. Trimmed and sized using the Lee dies about half of them wouldn't quite chamber without the bolt having to be roughly palmed closed. I adjusted the die and still had the same issue.
Next step I fireformed them using a 150 grain .308 cast and powder coated bullet with 10 grains of unique.
Accuracy was surprisingly good with 2" groups at 100 yards 6" to the right of point of aim with sights set for 400 yards.

The next sizing once again more than half of them didn't want to chamber hanging up on the case web where it seems to be oversize. I tried screwing the die down farther and it didn't seem to make any difference. I'm now on my third loads with this brass and still with the same issues. Accuracy has been outstanding and I'm not seeing any pressure signs nor am I close to max loads.
Once it's empty this time its going in the trash.

Just curious if anyone else has been using .284 win brass and having the same issues.

Been using Prvi brass to good effect. I am also reclaiming my GP11 brass and will attempt to reload these. CGN sponsor budget shooter supply has the correct primers. I am using the hydraulic method of decapping the berdan primers, then once I remove the crimps, I will resize, trim, prime and hope for the best. A long time reloader and mechanical guru friend suggested I use my prvi boxer load minus 1gr since the berdan primers are hotter.

 

[sunray]

The .284 starts out 25 thou under size in case head diameter, but 7 thou too big at the end of the case body. Suspect your cases never did get sized right and have simply bulged.

 

[Loki610]

The .284 starts out 25 thou under size in case head diameter, but 7 thou too big at the end of the case body. Suspect your cases never did get sized right and have simply bulged.

Ah that makes sense then. The amount of force to resize them was brutal. Damn near broke my workbench where the press is attached with a steel plate and 1" plywood

 

[diopter]

Use castor oil as resizing lube and go "over the top" after die bottoms out in the press.
Using a Rockchucker by any chance?
Your press may be flexing quite a bit.
Annealing the brass really helps.

 

[Loki610]

Use castor oil as resizing lube and go "over the top" after die bottoms out in the press.
Using a Rockchucker by any chance?
Your press may be flexing quite a bit.
Annealing the brass really helps.

Unfortunately just a lee classic cast, and I don't know know about the press flexing but the handle bent!