I had it in the sled with a bag of shot hanging on the barrel to reduce jump. So that would help keep the forearm from moving + I was holding on to the back of it. With that said, I didn't notice every time, but when I picked it up to shuck the shell, I did notice a couple times the chamber was open an inch or so.

So you're thinking it's unlocking the chamber/forearm as the slug is still in the barrel, causing slight movement thats affecting accuracy? Seeing if I'm on the same page here...

What about the BSA scope - seems like everyone is pretty unaminous on saying it's junk?