Bill,
Slow your 155 Sierra load down to 2,550 fps. I shoot that bullet out of my Swedish Mauser at that velocity and there has never been a ram rung even at ranges that are notorious for rung rams.
By slowing down the bullet you are improving the dwell time of the bullet as it blows up on the ram. This increased dwell time improves the bullet's ability to tip over a ram.
One other issue, what is your barrel's twist? If it is too slow your bullet will have a low actually BC due to bullet yaw. That translates into a very rapidly slowed bullet.
Regards,
Dan Theodore