Last week I blew primers out at the range. Figured it out and it was a bad ejector spring. Midway didn't have one available, so I took one off of my 30-06 to get me by.
100 rounds later, it happened again. I will be calling Jim tomorrow to order a few. What's causing this?

.260 shooting 142g smk, at 2750.
24" Shelien match barrel.