Last night I had 2 FTF using Herters steel case in my M&P 10. I have used other steel case and never had an issue.Maybe I was lucky before? Same ammo batch out of my PTR91 fired flawlessly. Both cartridges had what I would say were significant dents in the primer from firing pin. (I should have kept and took pictures)

 

I shoot a fair volume and buy bulk with all calibers so like to keep it cheap with the steel case. 

 

Anyone else have problems wiht Herters 308 or other calibers?

Anyone heard of issues with firing pin on M&P 10?

 

Reccomendations on steel case or Modification/upgrade on firing pin appreciated.

Do you still have them to photograph? Is the gun cleaned and lubed, including BCG and firing pin? I have no experience with herters but if the primer looks similar to those that fired I'd question the two rounds after considering my two q's.

Unfortuantely i did not photgraph or save them. Going to break the rifle down and do a full clean and inspection. Buddy gave me the ammo I have to replace. Was going to buy bulk of Tulammo. Wanted to find out if this gun is just known for issues with steel case before I buy a couple thousand rounds.

I've never heard of any issues with MP10 and ammo.

Herters is essentially repackaged Tulammo.  Maybe you had a few bad primers?  I had a handful duds with tula/herters/silver bear when I used to have my PTR91.  Fine for the range, but not for defense.