6.5 grendel resizing issue

[JamesIII]

I am full length resizing some starline 6.5 grendel cases after firing them through an AR15. It is everything I can do to get them resized, some I can not get the die all the way down to the shell holder. It appears to be trying to move brass to the base of the case, so much so that I can not finish the stroke. I thought I may have a chamber issue so I loaded up a hornady case with the same load, shot it in the same rifle and resized it. No problem! I have attached a pic of 2 starline cases, you can kind of see the ring at the bottom of the case. I have measured and compared everything I can think of with no luck. Btw these are lee pacesetter dies that I have used for a year. Took them apart and cleaned the heck out them. Any ideas will be much appreciated.
James3

[billy_56081]

Have you reloaded cases fired out of this rifle before? If not maybe an out of spec chamber.

[JamesIII]

I thought of that, that is why I reloaded the hornady case and fired it in the rifle for comparison. It could still be the rifle chamber and the hornady brass is just easier to work with. James

[JamesIII]

I carefully examined about 30 Of the starline cases and found some of them already have an expanded base before resizing. These are the problematic cases. Now my question is why just some of them? The case base is consistently expanded .004. All of these were shot slowly, no mag dumping. Could this be a hot load issue. I am loading a Hornady 123gr bthp over 27.9gr of IMR8208 with a CCI 41 primer. Other than loading I can think of no reason that only part of the cases would have the expanded base, all shot in the same rifle. James

[cwlongshot]

If your chamber is within spec, you may have excessively soft brass.
How does the base of the case look?
 Do you have extractor marks?
Maybe some lighter loads to start with that brass can work hard in a little bit.

Usually when I see things like that it's excessively overloaded Brass. .004 case it doesn't sound excessive but all rifles are different.
What's the velocity you're getting with that load?
I don't use that powder so I'm not familiar. But I shoot a lot of Grendel in Benchmark, AR comp & H335.