Had my first failures to return to battery today at the range. I was shooting some recently purchased Blazer Brass, 115gr FMJ in my 365XL. The first failure occurred after maybe thirty normal rounds and was the third round out of the freshly loaded magazine. I cleared that round and racked in the fourth which also failed to feed properly - failed to return to battery. So, I then ejected the magazine and cleared that round. The next five rounds fed and fired properly, however, the impacts were widely scattered, mostly off-right. After that the rest of the box, including the two that initially failed to feed, fired properly as did a handfull from another box. Other than the five scattered impacts I mentioned I was hitting consistently inside a two inch circle at 10 yds (thanks to my 507K!) so I'm reasonably sure those misses were ammo related.