I run the Champion Easy Hit Shotgun Fiber Optic Front Sight and just the mid bead in the back.
http://www.midwayusa.com/product/819512/champion-easy-hit-shotgun-fiber-optic-front-sight-3mm-red-5#reviewHead
Start low and work your way up. Load up 10 of each start at 4.0 then 4.2 and 4.4 Then chrono all of them and record the numbers to find out your power factor. The numbers in the book have never been close to right out of any guns that I tested. I bet you don't need to go to max load.
That's a hot load especially with a magnum primer. I would not shoot them. I would pull the bullets and put 4.3 gn of powder than shoot them with the magnum primer.
No it will not work with hammer down. You can heat the strap and mold it to work hammer down or place your order and call g-code with your order number and have them make the strap longer to work with hammer down.