What’s wrong ? Chamber, brass, dies

[Klem]

If the reamer is not exactly square with the bore then it's going to ream a cone. The Grendel profile is already a mild cone (see SAAMI blueprint), no doubt to aid extraction. But if the reamer goes in even slightly offset then the cone at the base is going to be more severe. That's what it seems like to me - too wide at the base, but still accurate. Regardless of accuracy, case life and safety are an issue - plus if the chamber was square to the bore it might even be more accurate.

Gas port drilled out of alignment and noticeable is extraordinary for that price.

Keep us posted please - Be interesting to know what happens.