Case shoulder deforming

[fast_pass88]

Tonight I was loading up some ammo for my 270 wsm and noticed a few rounds were a bit stiff while closing the bolt. Initially I assumed I didn't bump the shoulder back far enough when I full length resized, but I chambered some empty cases that were ready for powder and bullets and they chambered fine.

After further inspection I noticed the shoulders on the rounds I had seated bullets in were slightly deformed. Right at the shoulder it was actually wider then lower down on the case body. This is only one side of the case, the other side is flat as it should be. In the picture below I've held a straight edge against the side of the case and you can see there is a fairly large gap near the shoulder. all 20 rounds i loaded up are this way.

Any ideas as what would cause this during bullet seating? Maybe I'm cranking down too hard on my press? It's not a compressed load so there shouldn't be much pressure in there.
Any opinions or advice would be great!

[Desert Eagle]

There is a chance your seating die may be in too deep. Try resizing a case and see if it has the same effect. If it does, try adjusting sizing die upwards a bit and try again. Are your cases trimmed to length? Could possibly be a seating die with crimp hitting case and deforming...

Just a few ideas.

[gunluvr]

Can you describe how you set your seating die? Your shoulder seems to be getting crushed during bullet seating. Neck run out must be huge.

[Nystiri]

I had this happen on me while loading a couple of years ago. as far as I could tell, it was the neck being crushed by the seating die while seating the bullet. Strange part is is happened on random brass, I couldn’t find any correlations between them that would cause it to happen, and then just like that it stopped happening. I wound up just pulling the bullets, and resizing the brass back and started over. Odds are your bullets won’t be any good after this though. Mine got shredded on the process.

N

[elkhunter11]

As has been mentioned, it could be the seating die adjustment, but I had the same issue when helping a friend load some 270wsm, using his RCBS dies. The die was reducing the neck diameter too much, and the excessive neck tension was causing this. I added even more chamfer to the neck, but that didn't help, so I ended up having to use graphite on the inside of the neck and bullet, and seat the bullets in steps while rotating the case for each step. We managed to seat enough bullets for his test loads, but I brought my Redding dies along for the next loading session, and the issue disappeared , because the neck tension was much less.
How much effort did it take to seat the bullets? Wen I seated bullets after sizing with the RCBS dies, it took much more effort to seat the bullets, because of the excess neck tension.

[Grizzly Adams]

Sharp shoulders make problems. Betting this was a short mag before I read.

Grizz