gas blow back on Lapua 22-250 brass

[Dave T]

I am shooting Lapua brass in my 22-250. I fired this brass in a club match today and experienced gas blow back on the neck and all the way down the case body. This is the 3rd firing of this brass and it has not been full sized yet and I have never had this problem with this gun before. Before anyone wants to say your load is not sealing in the chamber and load isn't hot enough to get good seal, let me say I have fired this same brass with same load, and the load is not a mild load. I am wondering if this new Lapua brass is harder? Is it already hardened after only 3 firings? Anyone had this problem with 22-250 Lapua brass? Any help would be greatly appreciated.
Dave T

 

[ReedG]

I've only had that happen with extremely hard necks, which don't expand to seal the chamber. Annealing took care of it.

 

[Dave T]

I just recently shot Federal brass with same load with no problems.
Dave T