Sounds like there's too much distance betweer the receiver and the magazine. The bedding/inletting needs correction.

I just put a B&C stock on a Savage, and the receiver sat too high in the stock. The receiver did not touch the aluminum bedding block. I had to free float the tang, and remove a ton of material from the barrel channel. After I removed that material, the receiver could sink down into the stock like it was supposed to and rest on the aluminum bedding block. Even then, the recoil lug required bedding because it didn't touch anything. I had a different B&C stock a decade ago that needed the same thing done to it.

I bet your receiver sits too high in the stock like mine did, and needs to sit lower on the aluminum bedding block in order for the mag to feed properly. The mag is too far away from the bottom of the receiver. Search my recent posts, I did a big write up with pics last week about bedding a B&C stock.