hello everyone I just finished building a 6.5 Grendel. iv been working on some test loads to achieve maximum accuracy and performance so far I have tried 120gr Hornady a-max with 26GR of H335. they shot alright, they held a group within .75in at 100yds. I tried to load a batch of Hornady 129gr interlock. I used the same powder charge 26gr H335 and apon shooting them and inspecting the brass the primer had a small hole punched deep inside it and there was a large crater from the firing pin. I have never seen this before and I am not sure what the cause is. I know its from pressure but im not sure where its coming from. all my brass have had the same small mark on them about .25in down from the neck and I have not been able to fix it yet. I am hoping that maybe someone has seen these same issues and was able to fix it. im not sure if its from the loads I have been running on some were in the gun if anyone has an idea or has found a better load. the barrel has a 1-8 twist and i havnt found any load data for a Grendel with a 1-8 twist im hoping i just havn't been looking in the right place or someone has some info. thank you Robert.