Help!! I bought a DPMS LR-260 and it wont run!!

I have tried using the Cor-Bon REM 260 Scenars in 142gr and 139gr. neither will feed. It seems the bullets are striking the feed ramp and getting jammed, the bullet is actually being pushed into the shell....not good. I have tried several of the DPMS magazines as well as the Magul pul with no luck...Anyone have this problem and maybe a solution...Thanks in advance

Frustrated!!!