I had a brand new gen3 20sf with similar problems. Lucky for me I had a box full of spare parts that I started changing out one at a time. Ended up being the ejector. It was out of spec nicking the shell on the way in causing a nose up left side jam. Cheap part. Maybe 10-12 bucks. It might be the pbr has a slightly different shape making things worse. These guns should be very tolerant of different loads. This would explain your empty left in the breach face. Also the gen4 RSA seem to be stiffer than gen 3's. Most of gen3 that have feed RSA problems are with stiffer springs. You might try leaving the gun locked back for few days to lossen it up

Hey guys, just found this site. I've been over at glock talk for a few years now. My 20sf has at least 20k through it since I got it 3 years ago. I've shot boat loads of nosler 135's at 1500fps and lots of 200gr BT hard cast at 1230fps. The gun never gives me problems with the stock RSA. I while back I was having some feeding problems with 155gr SWC in a .40 conv, I upgraded to some wolf +10 mag springs and all was good. So I thought. I went back to my 200gr BT and started getting nose up Jams like your getting. I went back to new stock new mag springs and they ran perfect. The funny thing is the wolfs run good with all my other loads. When you start running max Sami spec loads the springs have to be matched almost perfect. That's why when you went with the heavier RSA things got worse. If its a pretty easy to feed profile I'd say your mag springs might be a little soft, new oem or wolfs might fix it.