I have a .577 hammerless Holland 3" BPE with steel barrels in excellent condition. Am contemplating using 75 grains of H4198 and backer rod with a 610 grain lead bullet. I used to use black powder many years ago in a Hammer Holland .577 3" BPE and haven't shot one since. I have Graeme Wright's new double rifle reloading book and really think smokeless is the way to go. Any horror stories out there about using backer rod vs Dacron? Any ringed chambers from using backer rod? I really like the idea of less recoil, no smoke and easier to regulate. Thanks for your input, I am no expert by any means!